-NRLF 


GIFT  OF 
L.    A.   Williams 


EDUCATION  DEFT. 


A  LABORATORY  MANUAL  FOR  WORK  IN 

GENERAL   SCIENCE 


BY 

OTIS  W.  CALDWELL,  W.  L.  EIKENBEEEY,  AND 
CHARLES  J.  PIEPER 

Tin:  SCHOOL  OK  KDUCATIOX,  THE  UNIVERSITY  OF  CHICAGO 


GINN  AND  COMPANY 

BOSTON'     •     NKW    YOIMv     •     CHICAGO     •     LONDON 
ATLANTA     •    DALLAS     •    COLUMBUS     •    SAN    FKANCISCO 


-toft 


EDUCATION  DEFT, 


COPYRIGHT,  1915,  BY 

OTIS  W.  CALDWELL,  \V.  L.  EIKEXBERRY 
AND  CHARLES  J.  PIEPER 


ALL   RIGHTS  RESERVED 
315.9 


Cftc   gtbenttum   jprcgg 

(.INN  ANIJ  COMPANY-  PKO- 
HRIETORS  •  BOSTON  •  U.S.A. 


PREFACE 

Laboratory  work  and  the  experiences  of  home  and  school  furnish  an  important  basis  for  the  course 
in  general  science.  The  following  outlines  for  experiments  and  demonstrations  have  been  developed 
so  as  to  include  the  exercises  which  have  proved  most  valuable  for  use  in  the  first  year  of  the  high 
school.  The  outlines  are  the  result  of  the  cooperative  work  of  several  high-school  teachers  through 
a  period  of  years,  and  have  been  tried  with  more  than  a  thousand  pupils.  Experiments  other  than 
those  here  included  have  been  tried,  bat  through  constant  trial,  elimination,  and  addition  the  work 
has  assumed  its  present  form. 

It  is  the  purpose  of  the  outlines  to  direct  the  pupils  into  the  habit  of  finding  out  about  many  kinds 
of  common  problems  in  science.  To  do  this  in  the  best  way  common  materials  are  used  for  experi- 
mentation, since  common  and  simple  phenomena  are  likely  to  be  more  educative  for  young  pupils 
than  those  which  are  uncommon  and  complex.  The  materials  needed  are  listed  in  connection  with 
each  exercise.  It  is  hoped  that  teachers  will  encourage  pupils  to  use  their  own  initiative  in  devising 
new  ways  to  perform  the  experiments,  as  well  as  in  working  out  additional  problems  which  are  sure 
to  be  suggested  in  the  discussion  of  the  experiments  here  outlined.  At  the  close  of  the  directions 
for  work,  one  or  more  additional  problems  are  suggested,  and  the  use  of  these  as  topics  for 
discussion  will  make  the  work  more  valuable. 

The  exercises  have  been  planned  so  that  each  one  requires  a  shorter  period  of  continuous  atten- 
tion than  is  usually  true  in  the  more  advanced  laboratory  work  in  high-school  science.  Experience 
has  shown  that  first-year  pupils  work  more  effectively  when  the  units  of  work  assigned  are  relatively 
short  and  definite.  This  plan  results  in  a  larger  number  of  exercises  than  would  be  used  in  a  more 
advanced  course  in. science.  In  many  cases,  however,  two  or  more  exercises  may  be  performed  in  a 
single  laboratory  period. 

Supplementary  or  alternative  experiments,  which  sometimes  require  more  complex  apparatus,  are 
often  given.  These  supplementary  experiments  are  indicated  by  the  same  arabic  number  as  the 
preceding  experiment,  but  with  a  letter  added.  Thus  22  A  is  an  experiment  which  may  be  used 
in  addition  to  or  instead  of  Exercise  22. 

When  diagrams,  charts,  or  graphs  are  called  for,  the  proper  kind  of  paper  for  such  work  is 
provided. 

The  Directions  to  Students  should  be  carefully  read  by  teacher  and  pupils.  These  directions,  in 
addition  to  giving  instructions  about  how  to  proceed,  are  designed  to  develop  interest  and  give  the 
proper  point  of  view. 

The  outlines  are  provided  in  both  bound  form  and  in  loose-leaf  form.  The  loose-leaf  form 
makes  it  possible  for  teachers  who  wish  to  vary  the  order  to  do  so. 

THE  AUTHORS 


[iii] 


CONTENTS 

EXKRCISK  PAGE 

1        Does  air  occupy  space  ? 1 

2.  Can  air  be  made  to  exclude  water  ? 2 

3.  Does  air  have  weight  ? 3 

3  A.  Does  air  have  weight  ? 4 

4.  How  much  does  a  cubic  foot  of  air  weigh  ? 5 

5.  Since  air  has  weight,  does  it  press  downward  as  other  heavy  objects  do  ? 6 

6.  Is  air  pressure  the  same  in  all  directions  ? 7 

7.  To  study  the  construction  and  operation  of  a  mercurial  barometer 8 

8.  What  effect  is  produced  upon  a  volume  of  air  by  a  change  in  its  temperature  ? 9 

8  A.   What  effect  is  produced  upon  a  volume  of  air  by  a  change  in  its  temperature  ? 10 

9.  How  are  mercury  thermometers  used  ? 11 

10.  What  is  the  relation  between  the  Fahrenheit  and  centigrade  thermometer  scales  ? 12 

10  A.  To  represent  graphically  the  relation  of  centigrade  and  Fahrenheit  scales 14 

11.  Does  the  sun's  position  at  noon  change  from  day  to  day  ? 15 

12.  To  determine  the  different  areas  covered  by  a  beam  of  light  striking  the  surface  of  the  earth  at 

different  angles 16 

12  A.  What  are  the  different  areas  covered  by  a  beam  of  light  striking  the  surface  of  the  earth  at 

different  angles  ?. 17 

13.  To  make  a  chart  which  will  show  graphically  the  length  of  day  and  night  at  various  times  of 

the  year 18 

14.  What  happens  to  water  vapor  when  it  comes  in  contact  with  a  cold  object  ? 19 

15.  What  is  the  temperature  at  which  the  water  vapor  condenses  in  the  room  ? 20 

16.  What  is  the  relative  humidity  in  the  room  ?  .     .     . 21 

17.  What  is  the  relation  between  air  pressure  and  wind  ? 22 

18.  In  what  direction  does  the  air  move  around  the  center  of  a  low-pressure  area  ? 23 

19.  What  effect  does  the  rotation  of  a  globe  have  upon  the  direction  of  motion  of  objects  on  its 

surface? 24 

20.  Is  air  compressible  ? 25 

21.  Do  gases  mix  with  one  another  ? 26 

22.  Will  gases  mix  with  one  another  if  the  lighter  gas  is  placed  above  the  heavier  one  ?     .     .     .     .  27 
22  A.  Do  liquids  diffuse  ? 28 

23.  Does  a  liquid  fill  all  the  space  which  it  appears  to  fill  ?. 29 

24.  What  are  the  parts  of  a  flame  ? 30 

25.  Do  the  parts  of  the  flame  differ  in  heat  ? 31 

26.  Of  what  is  the  central  part  of  the  flame  composed  ? '32 

27.  A  product  of  the  burning  candle 33 

28.  Is  water  a  simple  substance,  or  is  it  composed  of  more  than  one  simple  substance  ?       ....  34 
2i>.       What  is  the  nature  of  oxygen  —  the  less  abundant  gas  formed  in  the  decomposition  of  water?  36 

30.  What  is  the  nature  of  hydrogen  —  the  more  abundant  gas  formed  in  the  decomposition  of 

water?       38 

30  A.  Can  water  be  formed  by  burning  hydrogen  in  oxygen  ? 40 

31.  What  is  the  gas  given  off  by  a  burning  candle  ? 41 

32.  What  is  the  com  position. of  carbon  dioxide  ? 42 


EXERCISE  PAGE 

33.  What  are  some  of  the  properties  of  carbon  dioxide  ? 43 

34.  Can  the  green  coloring  matter  be  removed  from  leaves  ?  .          44 

35.  Is  there  a  food  material  in  the  leaf,  and  does  it  have  any  relation  to  chlorophyll  ? 40 

-36.      In  what  part  of  the  leaf  is  the  chlorophyll  ? 47 

37.  What  is  the  nature  and  use  of  the  outer  covering  of  the  leaf  ? 48 

38.  Is  there  a  waste  product  given  off  during  food  manufacture  ? 49 

39.  What  is  the  nature  of  the  gas  given  off  during  chlorophyll  work  ? 51 

40.  How  does  a  dependent  plant  live  ? 52 

41.  What  is  the  nature  of  the  yeast  plant  ? 53 

42.  What  effect  has  heat  upon  the  yeast  plant  and  fermentation  ? 54 

43.  How  do  bacteria  act  on  milk,  and  how  may  milk  be  preserved  from  such  action  ? 55 

44.  What  changes  in  volume  take  place  when  water  freezes  ? 58 

45.  What  happens  when  water  boils,  and  at  what  temperature  does  this  take  place  ? 60 

46.  How  is  water  distilled,  and  how  may  dissolved  solids  be  separated  from  water  ? 62 

47.  What  effect  has  evaporation  upon  temperature  ? 63 

48.  How  rapidly  does  water  evaporate  in  the  classroom  ? 64 

48  A.  Does  ice  evaporate  ? 65 

49.  How  rapidly  does  water  evaporate  from  a  plant  ? 66 

49  A.  Does  water  evaporate  from  a  plant  ? 68 

50.  How  does  a  siphon  work  ? 69 

51.  How  does  a  lift  pump  work  ? 70 

51  A.  How  does  a  pump  operate  ? 72 

52.  Is  the  lateral  pressure  in  water  different  from  the  pressure  downward  or  upward  ? 73 

53.  How  can  water  be  used  in  finding  the  volume  of  an  irregular  solid  ? 75 

54.  What  is  the  lifting  effect  of  water  upon  an  object  immersed  in  it  ? 76 

55.  Why  do  objects  float  in  water  ? 78 

56.  What  effect  does  Lake  Michigan  have  upon  the  temperature  of  places  near  it  ? 80 

57.  What  is  the  effect  of  Lake  Michigan  upon  the  surrounding  country  during  cold  winter  weather  ?  81 

58.  Is  there  a  difference  in  the  rates  at  which  soil  and  water  change  in  temperature  ? 82 

59.  What  are  the  principal  characteristics  of  harbors  and  waterways  ? 83 

60.  What  is  the  local  importance  of  water  transportation  ? 84 

61.  What  is  the  relation  between  water  supply  and  disease  ? 85 

61  A.  What  is  the  significance  of  the  local  death  rate  from  typhoid  ? 86 

61 B.  What  is  the  character  of  the  local  water  supply  ? 87 

62.  How  is  sewage  disposed  of  in  your  community  ? , 88 

63.  How  are  pulleys  used  as  machines,  and  what  are  the  advantages  of  different  systems  of  pulley 

arrangement  ? 89 

64.  How  to  measure  the  work  done  by  the  force  applied  in  a  pulley  system  in  raising  a  known 

weight  a  given  distance 91 

65.  How  much  work  is  done  upon  the  weight  (work  out)  in  Exercise  63  ? 93 

66.  What  is  the  efficiency  of  a  pulley  system  ? 94 

67.  Can  one  kind  of  energy  be  changed  into  another  kind  ? 95 

68.  What  is  the  principle  of  the  steam  engine  ? 96 

69.  What  is  the  nature  of  the  particles  which  make  up  the  soil  ? 97 

69  A.  What  is  the  character  of  that  part  of  the  soil  in  which  no  particles  can  be  seen  with  the 

unaided  eye  ? 98 

70.  How  much  water  may  be  held  by  soil  ? 99 

70  A.  What  is  the  water-retaining  capacity  of  different  kinds  of  soil  ? 101 

71.  Is  there  any  soluble  material  in  the  soil  ? 102 

72.  What  is  the  amount  of  organic  matter  in  soils  ? 103 

73.  How  are  soils  formed  ? 104 

74.  How  does  erosion  affect  soils  ? 105 

[vi] 


EXERCISE  PAGE 

75.  Can  the  roots  and  stump  of  a  plant  force  water  upward  ? 106 

76.  How  does  a  plant  absorb  water  ? 107 

77.  What  are  root  hairs  ? ...*....  109 

78.  What  is  the  path  of  water  in  plant  stems  ? Ill 

79.  '  What  food  materials  are  present  in  plants  ? ....112 

80.  Is  starch  soluble  in  water  ? 114 

81.  Can  starch  be  digested  (changed  into  a  soluble  substance)  outside  the  body  of  a  plant  or  animal  ?  115 

82.  How  is  food  distributed  through  the  human  body  ?  —  the  flow  of  blood  in  the  veins     ....  117 

83.  The  flow  of  blood  in  the  arteries 118 

84.  Of  what  does  the  blood  consist  ? 119 

85.  How  does  the  blood  circulate  through  the  capillaries  ? 120 

86.  What  are  the  values  of  different  kinds  of  foods  ? 121 

87.  What  are  the  stages  in  the  development  of  the  frog's  egg  ? 122 

88.  The  growth  and  development  of  a  tadpole 124 

88  A.  The  development  of  the  bird  embryo  during  the  hatching  of  the  egg 125 

89.  The  structure  of  a  seed  and  of  the  young  plant ..126 

90.  How  rapidly  may  plants  and  animals  increase  under  entirely  favorable  conditions  ?      ....  127 

91.  How  do  ears  of  corn  differ  in  the  number  of  grains  they  have  ? 129 

92.  How  do  ears  of  corn  differ  in  weight  ? 130 

93.  What  is  the  relation  between  the  weight  of  the  grains  and  that  of  the  cob  in  ears  of  corn  ?  .     .  131 

94.  Are  variations  in  parents  transmitted  to  offspring  ? 133 


[vii] 


APPARATUS    LIST 


It  is  believed  that  the  following  list  contains  all  the  apparatus  and  supplies,  excepting  a  few  very  common 
materials,  that  are  necessary  for  the  laboratory  work  in  general  science.  More  elaborate  apparatus  could  be  speci- 
fied in  many  cases,  but  it  is  believed  that  there  is  a  positive  educational  gain  in  using  simple  apparatus.  It  will 
be  noted  that  in  many  cases  it  is  possible  to  use  familiar  appliances  from  the  household,  farm,  and  shop,  and  these 
should  be  used  wherever  practicable.  It  is  taken  for  granted  that  the  school  possesses  certain  common  equipment 
such  as  hammer,  saw,  nails,  tacks,  pliers,  cork  and  rubber  stoppers,  and  glass  and  rubber  tubing. 

The  prices  attached  are  approximate  only  and  are  based  upon  retail  prices  as  found  in  retail  stores  and  in  dealers' 
catalogues.  Schools  should  be  able  to  secure  a  discount  of  from  10  to  25  per  cent  from  these  prices.  The  elimination 
of  the  most  expensive  pieces  of  apparatus  will  not  require  the  omission  of  many  exercises. 


GENERAL  APPARATUS 


1  air  pump  (if  the  laboratory  is  supplied  with  run- 
ning water,  it  will  be  cheaper  and  more  conven- 
ient to  use  a  filter  pump,  price  $1.75)  .  .  .  $4.00 

1  air-pump  platform 5.50 

1  or  more  aquaria  (battery  jars  may  be  used,  $0.65 

each) ." 65 

1  balance  (Harvard  trip  scale  or  other  balance  weigh- 
ing to  0.1  gram) 8.00 

1  set  balance  weights  (iron,  5  grams  to  1000  grains)   1.60 

1  bicycle  pump  for  inflating  football '25 

1  bladder  glass :  1.00 

1  barometer  tube 33 

1  ball  cord  (linen) 20 

1  piece  charcoal 

1  Ib.  copper  wire  (No.  18) 15 

1  roll  cotton  (absorbent) 20 

1  clarnp  (wire  test-tube  holder) 10 

3  (or  more)  dry  cells (50 

Maps  of  ports   or  waterways  of   local  importance. 

Price  lists  may  be  secured  from  the  following : 

Coasts    of    United    States :    Coast   and    Geodetic 

Survey,  Washington,  D.C. 
Great  Lakes :    United  States  Lake  Survey  Office, 

Detroit,  Michigan. 
Mississippi  River  :  Mississippi  River  Commission, 

St.  Louis,  Missouri. 

1  electrolysis  apparatus  (substitute  may  be  made 
from  bottle,  stopper,  and  electric-light  carbons 

as  described  in  Exercises) 1.25 

1  football  (borrow  this  from  athletic  department) 

1  funnel  (glass,  8  inches  in  diameter) 30 


100  filter  papers  (circular,  13  inches  in  diameter)      $0.70 
1  globe,  brass,  air-weighing  (glass  flask  may  be  sub- 
stituted)  2.50 

1  roll  labels  (Dennison's  perforated  paper  labels  No. 

221) 45 

1  or  more  magnifiers  ($0.50  each) 50 

1  Ib.  marble  chips 

1  meter  stick  or  yardstick 25 

1  osmometer,  Lyon's  pattern,  from  Win.  Gaertner 
and  Company,  Chicago  (glass  thistle  tube  may 

be  substituted) 50 

1  cake  paraffin  or  sealing  wax 05 

1  protractor  (brass,  5-inch) 20 

1  pail  (galvanized) 20 

1  glass  pump  model  (may  be  constructed  from  lamp 
chimney,  cork  stoppers,  wire,  leather,  and  tacks, 
as  described  in  Exercises) 1.65 

1  coil  picture  wire  (small) 05 

2  pinchcocks  (Mohr's  medium-si/e) 20 

1  pinchcock,  screw  compressor        20 

^  Ib.  parchment  paper,  medium  weight 20 

Reports  of  local  boards  of  health 

1  piece  sheet  rubber  (dentists'  rubber  dam,  2x2  ft.)      .25 

1  rubber  rod  or  ruler         10 

1  package  starch 10 

1  steam-engine  model 2.25 

4  thistle  tubes  (15-inch  stem) 48 

1  piece  tubing  (glass,  ^-irich  diameter,  5  foot  long)  .     .40 

1  wiro  basket  for  test  tubes 40 

Total $35.26 


[ix] 


INDIVIDUAL  APPARATUS 


uo 


One  or  more  sets  of  the  following  apparatus  will  be  needed.  Performance  of  experiments  by  individual  pupils 
when  practicable  will  require  that  the  apparatus  be  duplicated.  The  number  of  duplicate  pieces  needed  will  depend 
upon  the  number  of  pupils  in  the  classes  and  upon  whether  the  experiments  are  to  be  performed  by  each  pupil  working 
alone  or  by  groups  of  pupils. 

1  Bunsen  burner  (alcohol  lamps  may  be  used  if  the 

laboratory  is  not  supplied  with  gas)      .     .     .      $0.30 

2  bottles  (wide-mouthed,  6-  or  8-ounce) 10 

1  candle 05 

1  cup  (aluminum  drinking  cup,  polished  surface)      .     .10 
1  cylinder  (graduated,  100  cc.,  for  measuring  liquids)     .70 
1  flask  (glass,  6-ounce),  with  2-holed  rubber  stopper 

to  fit 25 

1  dish  (glass  or  earthenware,  3  or  4  inches  in  diam- 
eter, shallow  form  such  as  low  jelly  glasses)       .     .02 

1  drinking  glass 03 

1  pulley  (double) 45 

1  pulley  (single) 26 

1  pan  (granite  ware,  6  to  8  inches  in  diameter)    .     .     .10 


1  pan  (sheet-iron,  such  as  a  6-inch  frying  pan)     .      : 
^  doz.  plant  pots,  paraffined  paper  3   inches  high, 
^  cent  each.    (Earthenware  pots  may  be  used, 
but  must  be  sterilized  before  using  a  second 
time.    Paper  pots  are  thrown  away  after  using.) 
1  ring  stand  and  clamp  for  supporting  apparatus 
1  spring  balance,  reading  to  8  ounces  and  250  grams 
1  piece  tubing  (glass,  ^-inch  diameter,  18  inches  long) 
1  thermometer   (chemical)   reading  to   110°  C.   and 

220°  F 1.25 

1  vial  (shell  vial) 02 

Weather  maps  (free)  from  nearest  Weather  Bureau 
Station 

Total  (one  set) $5.90 


.03 
.90 
.80 
.10 


CHEMICALS 


1  bottle  ammonia  water  (household  ammonia)     .      $0.10 

1  Ib.  acid,  hydrochloric,  commercial 35 

1  Ib.  acid,  nitric,  commercial 35 

1  Ib.  acid,  sulphuric,  commercial 30 

1  qt.  alcohol,  grain,  95  per  cent 75 

1  oz.  eosin,  water  soluble  (red  ink  may  be  substituted)     .20 

£  Ib.  formaldehyde  (40  per  cent  solution) 20 

4  oz.  ether  (or  chloroform) 35 

4  oz.  Fehling's  solution  No.  1 
4  oz.  Fehling's  solution  No.  2 

(Mix  No.  1  and  No.  2  in  equal  parts  for  use.) 
4  oz.  iodine  solution  (tincture  of  iodine) 30 


Lime  water.  (Make  when  needed  by  slacking  lime 
in  water  and  filtering  off  the  water.  More  water 
may  be  added  to  the  residue  in  the  bottle  and  fil- 
tered off  later.  Keep  bottle  tightly  stoppered.) 

4  oz.  litmus  solution     .     .     .    - 

2  Ib.  mercury 2.00 

4  oz.  potassium  chlorate 10 

4  oz.  sulphur  (flowers) 05 

1  bag  salt  (coarse) 10 

4  oz.  vaseline 10 

1  Ib.  zinc  (granulated,  mossy,  or  scrap) 20 

Total $6.30 


SPECIAL  APPARATUS 

The  following  pieces  of  apparatus  can  be  secured  from  the  other  laboratories  of  the  school  if  these  are  fully 
equipped,  or  in  some  cases  they  may  be  borrowed  from  citizens  (these  pieces  are  not  used  with  sufficient  frequency 
to  justify  purchasing  for  the  general-science  courses  only)  : 

Compound  microscopes  or  micro-projection  apparatus,  slides,  cover  glasses. 

Steam  sterilizer.  (The  household  type  may  be  borrowed  and  is  as  satisfactory  as  the  laboratory  type.  A  sterilizer 
may  be  improvised  by  placing  the  object  to  be  sterilized  in  a  bucket  of  boiling  water.) 

A  slated  globe.    (May  be  secured  from  the  mathematics  department  or  geography  department.) 

The  expense  of  equipping  a  laboratory  for  general-science  classes  will  vary  according  to  the  amount  of  dependence 
placed  upon  the  laboratories  already  existing  in  the  building.  If  these  are  well  equipped  and  so  located  that  their 
facilities  can  be  used  to  the  fullest  extent,  very  little  new  apparatus  need  be  secured,  and  the  expense  will  be  nominal. 

If  it  is  desired  to  equip  the  general-science  laboratory  quite  completely  and  independently  of  other  departments, 
the  cost  is  essentially  as  follows,  assuming  that  the  school  has  secured  the  usual  discounts : 

1  complete  set  as  above  (not  providing  for  individual  laboratory  work  by  the  pupils) $40.00 

1  complete  set  and  19  duplicates  of  the  individual  set 130.00 

1  complete  set  and  duplicates  to  provide  for  ten  pupils  or  groups  of  pupils  working  simultaneously  on  many 

experiments 80.00 

By  borrowing  the  most  expensive  apparatus  and  pieces  used  only  once  or  twice  during  the  year  from  other  labora- 
tories and  by  improvising  some  pieces  as  suggested,  the  cost  of  equipment  for  a  very  satisfactory  course  with  a  large 
amount  of  individual  experimentation  may  be  reduced  to  $30.00  or  less. 


DIRECTIONS  TO   STUDENTS 

Each  observant  person  is  constantly  noting  occurrences  in  nature  which  he  would  like  to  have 
explained  to  him.  A  flying  kite  leads  us  to  ask  how  it  is  made  to  fly.  Boiling  water  in  a  kettle  lifts 
the  lid  which  covers  it,  and  we  want  to  know  what  causes  the  lid  to  rise.  The  tender  stem  of  a 
plant  pushes  up  through  gravelly  or  hard-packed  soil,  crowding  the  pebbles  and  soil  out  of  the  way, 
and  we  ask  how  the  delicate  shoot,  still  uninjured,  can  move  such  solid  bodies.  A  colony  of  ants 
makes  its  home  in  a  field  of  corn ;  the  corn  is  soon  retarded  in  its  growth,  and  we  want  to  know 
what  is  taking  place.  A  pupil  visits  a  friend  who  is  ill,  and  later  the  visitor  may  have  the  same 
disease  as  that  which  affects  the  friend.  What  has  occurred  ?  Many  such  questions  concern  our 
daily  lives,  and  we  are  more  intelligent  and  more  efficient  persons  when  we  can  answer  some  of  these 
questions. 

There  are  two  good  ways  of  securing  answers  to  our  questions.  One  way  is  to  ask  persons  who 
know  about  these  matters  or  to  read  what  they  may  have  written.  The  other  way  is  to  study  the 
occurrence  by  means  of  further  observation  and  experiment,  thus  trying  to  make  the  occurrence  itself 
help  to  answer  the  question  regarding  it.  It  is  the  purpose  of  these  outlines  to  use  the  latter  method 
in  answering  some  important  questions,  as  well  as  to  lead  to  new  questions. 

To  secure  the  greatest  good  from  an  experiment  it  is  necessary  (1)  to  record  the  way  in  which 
the  experiment  is  performed ;  (2)  to  state  the  facts  shown  by  the  experiment ;  and  (3)  to  explain 
these  facts,  if  an  explanation  can  be  made.  When  you  have  performed  an  experiment,  write  your 
statement  of  these  three  points  as  clearly  as  if  your  notes  were  intended  to  be  read  by  a  person 
who  knows  nothing  about  the  experiment  you  are  describing.  Make  diagrammatic  outlines  to  repre- 
sent the  apparatus  used,  whenever  such  diagrams  will  help  to  make  the  process  or  results  more  clear. 
In  all  cases  make  sure  that  your  work  is  concise,  neat,  and  clear  in  its  presentation  of  the  facts  and 
inferences  from  them. 


[xi] 


LABORATORY  MANUAL  FOR  WORK  IN 
GENERAL  SCIENCE 


EXERCISE  1 1      >   '  ^  j     ;;.";';•>•  >',><  A 
DOES  AIR  OCCUPY  SPACE? 

Materials.    A  jar,  a  deep  pan,  or  a  pail ;  a  drinking  glass. 

Directions.  In  a  large  jar  or  other  available  vessel  pour  water  until  the  vessel  is  about  three 
fourths  full;  then  hold  a  drinking  glass  mouth  downward  in  the  hand  and  while  holding  it  in  this 
position,  push  it  into  the  water  until  it  is  entirely  covered  with  water. 

Does  the  water  fill  all  of  the  space  within  the  glass  ? 

Tilt  the  glass  to  one  side,  and  observe  what  occurs.  Hold  the  glass  in  a  vertical  position  again, 
and  observe  the  level  of  the  water  inside.  Do  these  observations  help  to  solve  the  problem  of  this 
exercise  ? 

Additional  problem.    What  is  a  diving  bell,  and  how  does  it  work  ? 

1  As  stated  hi  Directions  to  Students,  page  xi,  each  pupil  should  note  exactly  what  is  done  in  the  performance  of  an  ex- 
periment, and  should  observe  what  occurs,  then  try  to  explain  what  has  occurred.  The  blank  space  following  the  directions 
is  for  use  in  recording  these  facts  by  means  of  sketches  and  descriptions. 


[1] 


EXERCISE  2 
TAX  AIR  BE  MADE  TO  EXCLUDE  WATER? 

Materials.  Those  of  Exercise  ;1 :,  also  a  short  glass  tube,  or  straw  bent  slightly  at  one  end,  or 
piece  of  rubber  tiiting.  • 

Directions.  I' hire  the  drmkinjg.'g.lass  under  the  water  so  that  it  is  full  of  water.  Then  invert  the 
glass  so  that  the  mouth  is  downward.  With  the  straw  or  tube  placed  with  the  bent  end  directly 
under  the  mouth  of  the  glass,  blow  through  the  tube.  Explain  what  occurs. 

Additional  problem.  Why  is  it  that  when  a  heavy  rain  falls  after  a  long  period  of  dry  weather  air  bubbles 
arise  from  the  soil  ? 


[2'] 


EXERCISE  3 
DOES  AIR  HAVE  WEIGHT? 

Materials.    A  football ;  a  bicycle  pump  ;  a  pair  of  balances. 

Directions.  Pump  into  the  football  all  the  air  which  can  be  forced  into  it  without  danger  of  burst- 
ing it.  Weigh  the  football  accurately  and  record  the  weight.  Open  the  tube  of  the  football  and  allow 
as  much  air  to  escape  as  can  be  done  without  allowing  the  football  to  collapse.  Weigh  accurately 
again.  Compare  and  explain  any  difference  between  the  two  weights. 

Additional  problem.  Do  you  think  that  a  given  volume  of  liquid  air  would  weigh  more  or  less  than  the 
same  volume  of  ordinary  air  ?  Why  ? 


[3] 


EXERCISE  3  A 
DOES   .VI  I{    HAVE  WEIGHT? 

Materials.    An  air  pump  (an  inexpensive  filter  pump  may  be  used)  ;  a  brass  globe  ;  a  bottle  or  flask. 

Directions.  This  experiment  may  be  performed  by  the  teacher, 
but  each  pupil  should  make  his  own  solution  of  the  problem  and 
write  complete  notes. 

Pump  the  air  out  of  a  brass  globe  or  other  container  as  com- 
pletely as  possible,  and  close  the  stopcock.  Weigh  and  record 
the  weight  of  the  globe.  Open  the  stopcock  to  admit  air,  weigh 
again,  and  record  the  weight.  Has  the  weight  changed? 

What  is  your  answer  to  the  question  with  which  this  exercise 
began  ? 

If  the  brass  globe  ordinarily  used  for  this  purpose  is  not 
available,  a  bottle  or  flask  may  be  used.  This  should  be  fitted 
with  a  one-holed  rubber  stopper,  through  which  is  inserted  a  short 
glass  tube.  A  piece  of  thick-walled  rubber  tubing  fitted  with  a 

pinch  clamp  will  serve  as  a  stopcock.  The  air  may  be  removed  by  means  of  either  an  ordinary  air 
pump  or  a  filter  pump.  The  latter  is  inexpensive  and  entirely  satisfactory  if  water  under  pressure 
is  at  hand. 


[4J 


EXERCISE  4 
HOW  MUCH  DOES  A  CUBIC  FOOT  OF  AIE  WEIGH?1 

Materials.    The  flask  used  in  preceding  exercise ;  a  graduated  cylinder  (or  a  foot  or  metric  rule). 

Directions.  Ascertain  the  cubic  contents  of  the  container  used  in  the  preceding  exercise.  If  the 
container  is  spherical  the  diameter  may  be  measured  and  the  volume  calculated ;  if  it  is  of  any  other 
shape  secure  the  volume  by  measuring  the  amount  of  water  necessary  to  fill  it.  Considering  this 
to  be  the  volume  of  the  air  in  the  container,  and  using  the  difference  in  weights  obtained  in  the 
preceding  work  as  the  weight  of  this  air,  calculate  the  weight  of  a  cubic  foot  of  air.  . 

In  your  notes  explain  your  method  of  work,  and  include  in  good  mathematical  form  each  step 
in  your  calculations. 

A  liter  of  air  weighs  about  1.293  grams.  A  cubic  foot  of  air  weighs  1.29  ounces  or  36.61  grams. 
Knowing  these  corrected  weights,  how  much  error  is  there  in  your  calculation  ?  How  do  you  explain 
the  difference  ? 

Additional  problem.    How  can  you  determine  the  weight  of  the  air  in  the  room  in  which  you  are  working  ? 

1  If  the  metric  units  of  measurements  are  desired  they  may  be  substituted  for  the  English  units.  Both  systems  of 
measurement  should  be  made  familiar  by  use. 


[5] 


EXERCISE  5 

SINCE  AIR  HAS  WEIGHT,  DOES  IT  PRESS  DOWNWARD  AS  OTHER 

HEAVY  OBJECTS  DO? 

Materials.  A  piece  of  sheet  rubber  (dentist's  rubber)  about  6  or  8  inches  square ;  a  bladder  glass 
("Elements  of  General  Science,"  Fig.  5);  an  air  pump  (or  a  filter  pump  as  described  in  Exercise  3  A, 
together  with  a  pump  platform). 

Directions.  Tie  a  piece  of  thin  sheet  rubber  across  the  top  of  a  bladder  glass.  When  the  rubber  is 
first  placed  upon  the  glass,  no  pressure  of  the  air  upon  the  rubber  is  noted,  because  there  is  air  both 
below  and  above  the  rubber.  In  order  to  know  whether  there  is  pressure  upon  the  rubber,  we  may 
remove  the  air  from  beneath.  To  do  this,  place  the  glass  upon  the  platform  of  an  air  pump  and 
remove  some  of  the  air. 

What  are  the  results  and  your  conclusions  ? 

Additional  problems.    Why  are  we  not  conscious  of  the  pressure  of  the  air  upon  us  ? 
With  a  hand  placed  over  the  bladder  glass  remove  some  of  the  air  from  the  glass.   Why  is  suction  not 
a  good  name  for  the  results  observed  when  the  air  is  partly  removed  from  beneath  the  hand  ? 


[6] 


EXERCISE  6 
IS  AIR  PRESSURE  THE  SAME  IN  ALL  DIRECTIONS? 

Materials.    Same  as  in  Exercise  5. 

Directions.  Using  the  same  experiment  as  in  Exercise  5,  pump  out  part  of  the  air  and  then  close 
the  stopcock  so  that  no  air  can  enter.  Turn  the  apparatus  on  its  side,  and  also  upside  down.  In  each 
case  note  whether  the  rubber  is  bulged  inward  in  the  same  way  and  to  the  same  extent.  What  is 
your  conclusion  ? 

Additional  problems.  Why  does  not  the  downward  pressure  of  the  air  force  a  bucket  or  other  object 
from  one's  hand? 

What  causes  a  rubber  or  leather  "  sucker  "  to  adhere  to  a  smooth  surface  ?  Will  it  adhere  more  readily 
to  a  smooth  or  a  rough  surface  ?  Why  ? 


[7] 


EXERCISE  7 
TO  STUDY  THE  CONSTRUCTION  AND  OPERATION  OF  A  MERCURIAL  BAROMETER 

Materials.  Glass  tube  about  one-quarter  inch  in  diameter  and  32  or  33  inches  in  length;  a 
pound  of  mercury ;  a  dish  2  to  3  inches  in  diameter. 

Directions.  The  teacher  may  construct  a  barometer  before  the  class  as  follows :  Cut  a  glass  tube 
about  32  or  33  inches  long.  One  end  of  the  tube  should  be  closed,  which  may  be  done  by  heating 
until  it  melts.  Fill  the  tube  with  mercury.  Closing  the  tube  with  a  finger,  invert  it  in  a  cup  of 
mercury.  When  the  finger  is  removed,  measure  the  height  of  the  mercury  in  the  tube  above  the 
level  of  the  mercury  in  the  cup.  What  supports  the  mercury  ?  How  could  this  apparatus  be  used 
to  measure  the  weight  of  the  air  in  different  places  and  at  different  times  ? 

Barometers  constructed  hurriedly  as  above  are  not  accurate  because  some  air  bubbles  adhere  to 
the  glass  and  finally  get  into  the  space  above  the  mercury.  In  a  well-constructed  barometer  this  air 
has  been  driven  out.  Such  a  one,  with  graduation  showing  the  height  of  the  column  in  inches  or 
centimeters,  should  be  on  the  wall.  It  should  be  examined  from  day  to  day  and  a  record  kept. 

Additional  problems.  In  what  ways  and  for  what  reasons  will  the  column  of  mercury  change  when  the 
barometer  is  taken  high  into  the  air  or  down  into  a  deep  mine  ? 

If  the  column  of  mercury  in  a  barometer  is  30  inches  high  at  sea  level,  how  high  will  the  column  be 
at  an  elevation  which  has  half  as  great  air  pressure  as  at  sea  level  ? 

Incline  the  barometer  tube  to  one  side.  Then  measure  the  length  of  the  mercury  column,  and  also  the 
vertical  height  of  the  upper  end  of  the  mercury  above  a  point  at  the  same  level  as  that  of  the  mercury  in 
the  dish.  Explain  the  results. 


[8] 


EXERCISE  8 

WHAT  EFFECT  IS  PRODUCED  UPON  A  VOLUME  OF  AIR  BY  A  CHANGE 

IN  ITS  TEMPERATURE? 

Materials.  A  glass  flask  or  bottle ;  a  one-holed  rubber  stopper  which  fits  the  flask  or  bottle ;  a 
glass  tube  about  18  inches  in  length ;  a  drinking  glass  or  other  similar  vessel. 

Directions.  Insert  one  end  of  the  glass  tube  through  a  one-holed  rubber  stopper,  then  place  the 
stopper  in  the  neck  of  the  flask  or  bottle.  Hold  the  apparatus  in  an  inverted  position  with  the  free 
end  of  the  tube  in  a  vessel  of  water.  Warm  the  flask  with  the  hands.  What  occurs  ?  Keep  the  hands 
on  the  flask  as  long  as  there  is  any  result.  Then  remove  the  hands,  but  keep  the  end  of  the  tube 
under  water  and  allow  the  flask  to  cool,  noting  what  happens. 

Explain  the  results  you  have  seen.  What  have  you  learned  about  the  behavior  of  air  when 
heated  ?  when  cooled  ? 

Additional  problems.  When  an  automobile  tire  has  been  pumped  full  of  air  in  the  early  morning  and 
then  allowed  to  stand  in  the  sunlight  for  some  hours,  it  sometimes  bursts.  Why  ? 

One  type  of  glass  fruit  jar  is  sealed  by  applying  the  cap  to  the  jar  while  the  jar  and  contents  are  hot, 
the  cap  not  being  screwed  or  clamped  to  the  jar.  What  holds  the  cap  on  the  jar  ? 

Could  the  flask  and  tube  of  the  above  exercise  be  used  as  a  thermometer  ? 


EXERCISE  8  A 

WHAT  EFFECT  IS  PRODUCED  UPON  A  VOLUME  OF  AIR  BY  A  CHANGE 

IN  ITS  TEMPERATURE? 

Materials.  A  toy  balloon  well  inflated ;  a  refrigerator  (may  be  made  by  placing  a  piece  of  ice  in 
a  covered  box  or  pail) ;  one  of  the  schoolroom  radiators,  hot-air  register,  or  a  heating  stove. 

Directions.  Measure  the  circumference  of  the  balloon  accurately.  Record  the  measurement.  Place 
the  balloon  in  the  refrigerator  for  fifteen  minutes,  then  quickly  measure  the  same  circumference  again, 
and  record.  Then  place  the  balloon  above  the  radiator,  register,  or  stove  for  fifteen  minutes  and  meas- 
ure in  the  same  way  again.  Compare  the  three  sets  of  measurements,  and  explain  any  differences. 

Additional  problems.    Balloonists  report  that  when  a  cloud  remains  between  a  balloon  and  the  sun  for  a 
time,  the  balloon  begins  to  descend,  and  ascends  again  when  the  sunshine  falls  upon  the  balloon.    Explain. 
Why  do  balloonists  find  it  difficult  to  remain  afloat  at  night  ? 


[10] 


EXERCISE  9 
HOW  AEE  MERCURY  THERMOMETERS  USED? 

Materials.    Some  common  thermometers,  either  Fahrenheit  (F.)  or  centigrade  (C.). 

Directions.  The  bright  material  in  the  thermometer  is  mercury  (or  quicksilver).  See  how  far  up 
the  tube  the  mercury  extends  from  the  bulb.  What  happens  if  you  warm  the  thermometer  in  the 
hands  or  by  holding  it  above  a  stove  ?  if  you  cool  it  ?  Do  you  get  a  quick  result  better  by  warming 
the  stem  or  the  bulb  ?  Why  ?  For  what  reason  are  thermometers  always  made  with  bulbs  ?  What 
have  you  learned  about  the  action  of  mercury  when  its  temperature  changes  ? 

Additional  problems.  What  is  the  temperature  of  your  schoolroom  at  your  desk  ?  at  the  open  window  ? 
near  the  heating  apparatus  ? 

If  you  have  a  thermometer  the  bulb  of  which  can  be  placed  in  your  mouth,  determine  the  temperature 
of  your  body. 


[11] 


EXERCISE  10 

WHAT  IS  THE  RELATION  BETWEEN  THE  FAHRENHEIT  AND  CENTIGRADE 

THERMOMETER  SCALES? 

Materials.    Fahrenheit  and  centigrade  thermometers ;  cups  half  filled  with  water. 

Directions.  Two  persons  may  work  together.  They  must  have  a  centigrade  and  a  Fahrenheit 
thermometer.  Place  both  of  these  in  water,  and  read  both  at  the  same  time  without  removing  them 
from  the  water.  Record  the  readings  in  two  parallel  columns  below,  placing  readings  made  at  the 
same  time  opposite  each  other.  After  either  warming  or  cooling  the  water,  record  the  readings  again. 
Do  this  for  five  or  six  different  temperatures,  recording  your  results.  If  possible,  use  a  mixture  of 
ice  and  water  for  one  of  the  trials  and  hot  water  (almost  boiling)  for  another. 

The  relation  between  the  two  scales  can  be  determined  by  comparison  of  any  two  sets  of  readings. 
What  is  the  number  of  divisions  (degrees)  on  the  Fahrenheit  scale  between  your  highest  and  lowest 
readings  ?  What  is  the  number  of  degrees  on  the  centigrade  scale  between  the  corresponding  read- 
ings ?  On  which  scale  is  the  number  of  degrees  between  the  two  points  the  greater  ?  A  single 
degree  on  the  centigrade  scale  is  equivalent  to  how  many  degrees  on  the  Fahrenheit? 

Check  your  results  by  calculating  from  any  other  two  sets  of  readings  and  by  reference  to  your 
textbook. 


c. 


F. 


Additional  problems.  The  temperature  of  the  human  body  is  usually  about  98.6°  F.  What  is  the  tem- 
perature in  the  centigrade  scale  ? 

The  usual  temperature  of  a  good  living  room  is  about  20°  C.  AVhat  is  the  temperature  in  the  Fahrenheit 
scale  ? 


[12] 


EXERCISE  10  A 

TO  REPRESENT  GRAPHICALLY  THE  RELATION  OF  CENTIGRADE  AND 

FAHRENHEIT  SCALES 

Materials.  A  sheet  of  cross-section  paper  (paper  ruled  in  two  directions  at  right  angles) ;  the 
data  from  Exercise  10. 

Directions.  On  the  accompanying  sheet  of  cross-section  paper,  the  heavy  horizontal  lines  are 
numbered  to  represent  the  Fahrenheit  scale.  The  lowest  heavy  line  represents  30°,  the  next  one 
40°,  and  so  on  to  the  top  of  the  paper.  Each  light  line  thus  represents  one  degree.  Similarly  the 
vertical  lines  represent  the  centigrade  scale. 

Place  a  point  at  the  intersection  of  the  line  representing  212°  F.  with  the  line  representing 
100°  C.  This  point  represents  the  following  relation : 

212°  F.  =  100°  C. 
Locate  another  point  to  represent  the  following : 

32°  F.  =  0°  C. 

Draw  a  straight  line  through  these  two  points  from  one  margin  of  the  paper  to  the  other.  If  accu- 
rately constructed,  this  line  may  be  used  as  a  means  of  transferring  readings  from  one  scale  to  the 
other.  For  instance,  if  the  temperature  of  the  room  is  22°  C.,  the  Fahrenheit  equivalent  may  be  found 
as  follows :  Follow  the  22°  C.  line  upward  to  its  intersection  with  the  diagonal  line.  From  the  point 
of  intersection  follow  the  nearest  horizontal  line  to  the  left  side  of  the  page  and  read  off  its  value  in 
the  Fahrenheit  scale.  Reverse  the  process  to  change  from  Fahrenheit  to  centigrade. 

Place  on  the  page  points  to  represent  each  pair  of  readings  secured  in  the  preceding  exercise. 
The  distances  by  which  they  are  separated  from  the  diagonal  line  are  due  to  inaccuracies  in  your 
observations  or  in  the  thermometers. 

Preserve  this  sheet  and  use  it  to  change  temperature  readings  from  one  scale  to  the  other. 


[14] 


EXERCISE  10A 


220°  F. 


210 


2OO 


190 


1O  2O  3O  4O  5O  6O  7O  8O  9O  1OO  110       120°  C 


—2O        — 1O 


EXERCISE  11 
DOES  THE  SUN'S  POSITION  AT  NOON  CHANGE  FEOM  DAY  TO  DAY  ? 

Materials.    A  piece  of  cardboard  about  10  inches  square. 

Directions.  The  members  of  the  class  should  work  together  on  this  exercise,  but  each  pupil 
should  write  notes  independently. 

Place  a  large  piece  of  cardboard  with  a  hole  about  three  eighths  of  an  inch  in  diameter  in  the  upper 
part  of  a  south  window  and  fasten  it  securely  in  place.  When  the  sun  is  shining  brightly  notice  on 
the  floor  or  desk  the  spot  of  light  made  by  the  sun  shining  through  the  hole  in  the  cardboard.  Trace 
the  position  of  the  spot  on  the  floor  with  a  pencil  or  crayon  at  intervals  of  five  minutes.  On  the  next 
or  some  succeeding  day,  at  the  same  hour,  note  whether  the  spot  is  at  the  same  distance  from  the 
window  as  at  first.  If  not,  what  does  this  indicate  regarding  the  change  in  elevation  of  the  sun  in 
the  sky  ? 

Additional  problems.  Why  is  it  that  when  you  trace  slowly  the  spot  of  light  referred  to  above,  your  mark 
when  you  finish  does  not  coincide  with  the  mark  with  which  you  began  ? 

If  in  performing  the  above  experiment  the  spot  of  sunlight  moved  farther  from  the  window  or  nearer 
to  it,  do  you  think  the  direction  of  this  movement  would  be  the  same  for  twelve  months  ?  Why  ? 


[15] 


EXERCISE  12 

TO  DETERMINE  THE  DIFFERENT  AREAS  COVERED  BY  A  BEAM  OF  LIGHT  STRIKING 
THE  SURFACE  OF  THE  EARTH  AT  DIFFERENT  ANGLES. 

Materials.    Some  small  blocks  of  wood  6  or  8  inches  long  and  1  inch  square ;  a  saw  ;  a  protractor. 

Directions.  Suppose  that  at  one  time  of  the  year  the  sun's  rays  fall  at  an  angle  of  72.5°,  and 
25.5°  at  another  time  of  the  year.  Cut  one  end  of  a  block  of  wood  at  an  angle  of  72.5°  and  the 
other  end  of  the  block  of  wood  at  an  angle  of  25.5°.  Then  place  each  slanting  end  of  this  block  on 
cross-section  paper  and  trace  the  area  covered  by  each  of  the  ends.  What  are  the  corresponding 
areas  covered  by  the  two  ends  of  the  block  ?  How  many  times  larger  is  one  than  the  other  ? 
Which  is  the  larger?  If  a  beam  of  light  1  inch  square  falls  at  an  angle  of  72.5°  and  another 
at  25.5°,  which  will  have  the  greater  heating  effect  on  1  square  inch  of  surface  ?  How  many  times 
greater  ?  Why  ? 

Additional  problems.  How  are  the  facts  of  the  above  experiment  related  to  the  changes  of  seasonal 
temperatures  ? 

When  the  lights  of  automobiles  or  bicycles  approach  a  gateway  or  doorway,  are  the  upright  posts  or  the 
roadway  between  them  the  more  brilliantly  lighted  ?  Why  ? 


[16] 


EXERCISE  12A 

WHAT  ARE  THE  DIFFERENT  AREAS  COVERED  BY  A  BEAM  OF  LIGHT  STRIKING  THE 
SURFACE  OF  THE  EARTH  AT  DIFFERENT  ANGLES? 

Materials.    The  representation  of  angles  shown  on  this  sheet. 

Directions.  Let  the  horizontal  line  in  the  figure  below  represent  the  surface  of  the  earth.  Line  a 
is  drawn  so  that  it  makes  an  angle  of  72.5°  as  labeled,  and  line  b  makes  an  angle  of  25.5°.  These  are 
approximately  the  angles  which  the  sun's  beams  make  in  summer  and  winter,  respectively,  at  a  lati- 
tude of  41°.  Draw  a  line  parallel  to  line  a  at  a  distance  of  2  centimeters  from  it.  The  length  of  the 
base  line  between  the  two  intersections  will  then  represent  the  length  of  a  rectangular  area  covered  by  a 
beam  of  light  2  centimeters  square.  Taking  this  line  as  the  length  of  the  rectangle,  complete  the 
rectangle  below  the  line,  making  it  2  centimeters  wide.  Calculate  from  its  dimensions  the  number  of 
square  centimeters  covered  by  a  beam  of  light  2  centimeters  square  striking  the  earth's  surface  at  an 
angle  of  72.5°. 

Draw  a  line  parallel  to  line  b  and  2  centimeters  from  it ;  let  the  length  of  the  base  line  between 
the  two  intersections  represent  the  length  of  the  area  covered  by  a  beam  of  light  striking  the  earth 
at  an  angle  of  25.5°.  Using  the  width  of  the  beam  as  2  centimeters,  complete  the  rectangle  and 
calculate  the  area. 

What  do  you  conclude  from  the  above  work  ?  How  many  times  larger  than  the  first  area  is  the 
area  covered  by  the  beam  striking  the  earth  at  an  angle  of  25.5°  ?  Why  is  it  warmer  in  summer 
than  in  winter? 


25} 


[17] 


EXERCISE  13 

TO  MAKE  A  CHART  WHICH  WILL  SHOW  GEAPHICALLY  THE  LENGTH  OF  DAY   AND 

NIGHT  AT  VAKIOUS  TIMES  OF  THE  YEAR 

Materials.  Cross-section  paper ;  a  ruler ;  an  almanac  giving  time  of  sunrise  and  sunset  through- 
out the  year. 

Directions.  On  the  cross-section  paper  draw,  in  heavy  black  lines,  as  near  as  possible  to  the 
center  of  the  page,  a  rectangle  13  centimeters  high  and  12  centimeters  wide.  This  should  follow  the 
heavy  centimeter  lines.  Let  the  vertical  centimeter  lines  represent  the  even  hours  of  the  day  from 
midnight  to  midnight,  and  they  should  be  so  labeled.  The  horizontal  centimeter  lines,  except  the  top 
and  bottom  lines,  will  represent  the  first  days  of  the  twelve  months.  They  should  be  labeled  by 
writing  the  names  of  the  months  to  the  left  of  the  rectangle,  opposite  the  proper  lines. 

Find  from  an  almanac  the  time  of  sunrise  and  sunset  for  the  first  day  of  each  month,  and  mark 
the  points  which  will  correspond  to  these  hours  on  the  proper  month  lines.  Ink  those  portions  of 
the  lines  which  represent  night.  When  you  have  completed  the  chart  examine  it  and  state  care- 
fully what  conclusions  you  may  draw  from  it. 

Can  you  give  a  reason  for  the  change  of  hours  of  sunshine  and  darkness  ? 

Additional  problem.  What  is  the  length  of  the  longest  and  of  the  shortest  periods  of  daylight  at  the 
equator  ?  at  the  tropic  of  Cancer  or  of  Capricorn  ?  at  the  arctic  circle  ?  at  one  of  the  poles  ? 


[18] 


EXERCISE  13 


EXERCISE  14 

WHAT  HAPPENS  TO  WATER  VAPOR  WHEN  IT  COMES  IN  CONTACT  WITH 

A  COLD  OBJECT? 

Materials.    A  polished  metal  cup,  preferably  aluminum,  or  a  new  tin  cup ;  ice ;  salt. 

Directions.  Place  water  which  has  approximately  the  temperature  of  the  room  in  a  bright  metal 
cup.  Add  ice  or  snow  to  the  water.  While  the  water  is  cooling  watch  for  any  deposit  on  the  outer 
surface  of  the  cup.  What  is  the  deposit  ?  Where  did  it  come  from  ?  Why  is  there  not  a  similar 
deposit  on  other  objects  in  the  room  ?  If  all  of  the  air  in  the  room  were  cooled  to  the  temperature 
of  the  air  in  contact  with  the  cup,  what  would  happen  ? 

NOTE.  If  no  deposit  is  obtained  above,  a  lower  temperature  may  be  secured  by  adding  a  handful  of  salt 
to  the  ice  and  water  mixture. 

Additional  problems.  When  a  person  who  wears  glasses  goes  from  the  cold  out  of  doors  into  a  warm 
room,  the  glasses  often  become  u  cloudy."  Why  ? 

What  causes  the  moisture  to  collect  in  summertime  upon  a  glass  or  pitcher  of  ice  water  ? 
What  is  dew  ?    What  causes  it  to  appear  ? 


[19] 


EXERCISE  15 

WHAT  IS  THE  TEMPERATURE  AT  WHICH  THE  WATE.R  VAPOR  CONDENSES 

IN  THE  ROOM? 

Materials.    Same  as  in  Exercise  14  ;  the  table  on  page  23,  "  Elements  of  General  Science." 

Directions.  Use  the  same  apparatus  as  used  in  Exercise  14.  Record  the  temperature  of  the  room. 
Stir  the  mixture  of  ice  and  water  with  a  thermometer.  Do  not  allow  your  breath  to  come  in  contact 
with  the  cup.  When  the  first  clouding  of  moisture  appears,  read  the  thermometer  and  record  the 
temperature.  Now  remove  the  ice  or  snow  and  allow  the  cup  to  warm.  When  the  last  traces  of 
moisture  disappear,  read  the  thermometer  again  and  record.  Make  several  trials,  and  average  all 
readings.  If  your  work  has  been  accurate,  this  average  reading  is  the  approximate  dew  point  (satura- 
tion temperature)  of  the  water  vapor  in  the  room  at  the  time  when  the  experiment  was  performed. 

What  was  the  temperature  of  the  room  ?  Was  the  air  in  the  room  saturated  at  that  time,  or  at 
what  temperature  would  it  have  been  saturated  ? 

Additional  problems.  By  reference  to  the  table  in  the  text  find  the  weight  of  water  vapor  per  cubic  foot 
present  in  the  room  at  the  time  of  the  experiment.  This  is  the  absolute  humidity. 

What  is  the  weight  of  the  water  vapor  in  the  entire  room  in  which  you  are  working  ? 


[20] 


EXERCISE  16 

WHAT  IS  THE  RELATIVE  HUMIDITY  IN  THE  ROOM? 

Materials.  Data  from  the  preceding  exercise ;  the  table  on  page  23,  "  Elements  of  General 
Science." 

Directions.  From  the  preceding  exercise  (Additional  problems)  obtain  the  weight  of  water  vapor 
per  cubic  foot  of  space  in  the  room  at  the  time  the  experiment  was  performed.  Refer  to  the  table  to 
find  out  what  weight  of  water  vapor  per  cubic  foot  of  space  would  have  been  present  if  the  space 
had  been  saturated  at  the  temperature  observed  at  the  time  of  the  experiment.  What  percentage  of 
the  latter  weight  was  the  weight  of  water  actually  present  ?  This  was  the  relative  humidity.  Write 
a  definition  of  the  term  relative  humidity.  State  the  difference  between  relative  and  absolute 
humidity. 

Additional  problems.  When  raindrops  are  forming  and  falling  from  the  atmosphere,  what  is  the  relative 
humidity  of  the  atmosphere  ? 

It  is  sometimes  said  that  the  air  in  artificially  heated  rooms  is  like  the  air  of  a  desert.  By  determining 
the  relative  humidity  in  the  classroom  on  each  of  several  days,  see  what  basis  there  is  for  this  statement. 
How  can  this  condition  be  changed  ? 


[21] 


EXERCISE  17 
WHAT  IS  THE  RELATION  BETWEEN  AIR  PRESSURE  AND  WIND? 

Materials.  A  supply  of  daily  weather  maps,  usually  obtainable  in  sufficient  quantity  from  the 
nearest  United  States  Weather  Bureau  Station.  By  writing  to  the  Weather  Bureau,  Washington,  D.C., 
one  may  obtain  a  special  bulletin  entitled  "  Explanation  of  the  Weather  Map." 

Directions.  The  teacher  and  students  should  study  together  a  daily  weather  map  and  become 
familiar  with  the  characters  used  to  represent  weather  conditions.  An  explanation  of  these  characters 
is  printed  on  the  map. 

Select  a  map  with  a  well-defined  low-pressure  area  similar  to  the  maps  on  page  31  of  the 
"  Elements  of  General  Science."  Study  the  wind  direction  as  shown  by  the  arrows  around  the  low- 
pressure  center.  How  many  arrows  indicate  winds  blowing  (a)  toward  a  lower  pressure  ?  (6)  toward 
a  higher  pressure  ?  (Arrows  pointed  as  .if  to  cross  the  isobar  toward  the  lower  pressure,  though  not  at 
right  angles,  are  to  be  counted  in  («).)  In  what  percentage  of  the  whole  number  of  cases  studied 
does  the  wind  blow  from  a  high-pressure  area  to  a  low-pressure  area  ? 

What  is  your  answer  to  the  question  of  this  exercise  ? 

Additional  problems.  What  conditions  of  air  pressure  over  the  United  States  would  cause  a  warm  wind 
from  the  south  ? 

By  study  of  weather  maps  for  several  successive  days,  see  if  you  can  determine  the  usual  direction  and 
average  daily  distance  traveled  by  high  and  low  pressures. 


[22] 


EXERCISE  18 

IN  WHAT  DIRECTION  DOES  THE  AIR  MOVE  AROUND  THE  CENTER  OF  A 

LOW-PRESSURE  AREA? 

Materials.    Weather  maps  used  in  preceding  exercise. 

Directions.  In  the  part  of  the  map  used  in  the  preceding  exercise,  consider  only  those  arrows 
included  in  (a),  and  determine :  (1)  how  many  of  these  arrows  which  indicate  that  the  wind  blows 
inward  are  there  which  cross  the  isobar  perpendicularly ;  (2)  how  many  arrows  turn  to  their  right 
of  a  line  perpendicular  to  the  isobar ;  (3)  how  many  arrows  turn  to  their  left.  What  percentage 
of  the  arrows  turn  to  their  right  ?  What  does  this  result  show  about  the  general  direction  of  the 
wind  in  a  "  low  "  ?  Make  a  diagram  about  2  inches  in  diameter,  showing  the  wind  direction  about 
a  "  low."  Is  this  direction  clockwise  or  counterclockwise  ? 

Additional  problem.  If  a  "low"  were  to  pass  eastward  across  the  country  along  a  path  lying  north  of 
you,  what  changes  in  wind  direction  would  be  experienced  in  your  locality  ?  What  changes  would  there 
be  if  it  passed  south  of  you  ? 


[23] 


EXERCISE  19 

WHAT  EFFECT  DOES  THE  ROTATION  OF  A  GLOBE  HAVE  UPON  THE  DIRECTION  OF 

MOTION  OF  OBJECTS  ON  ITS  SURFACE? 

Materials.  A  globe  (preferably  a  slated  globe)  mounted  so  that  it  may  be  rotated  readily ;  a 
pitcher  or  dish  of  water. 

Directions.  Place  the  globe  in  a  position  with  its  axis  vertical.  With  the  globe  stationary  pour 
a  little  water  on  its  upper  end,  which  may  be  marked  "  north  pole."  Note  that  the  water  flows  to 
the  other  pole.  Its  path  is  like  a  meridian. 

After  drying  the  globe^  rotate  it  in  the  direction  in  which  the  earth  rotates  —  west  to  east. 
Pour  a  little  water  on  the  globe  while  rotating.  When  it  has  come  to  rest  note  the  path  which 
the  water  made.  Is  its  path  a  meridian  of  the  globe  ?  Does  it  curve  to  its  right  or  to  its  left  on 
the  upper  half  (northern  hemisphere)?  Does  it  curve  to  its  right  or  its  left  on  the  lower  half 
(southern  hemisphere)  ? ' 

If  this  holds  good  for  the  earth  as  well  as  for  a  small  globe,  what  are  your  conclusions  about 
the  effect  of  the  earth's  rotation  upon  the  direction  of  the  winds  ?  What  have  you  seen  upon  the 
weather  map  which  agrees  or  disagrees  with  this? 

Additional  problem.  Can  you  determine  what  would  be  the  prevailing  direction  of  the  wind  if  the  earth 
did  not  rotate  ? 


[24] 


EXERCISE  20 


IS  AIR  COMPRESSIBLE? 

Materials.  Glass  tubing  -1  inch  in  diameter ;  a  small  glass  funnel ;  rubber  tubing  to 
tubing ;  pinch  clamp  ;  small  wire  ;  mercury. 

Directions.  Bend  a  5-foot  length  of  glass  tubing  to  make  a  U-shaped  tube  with  the 
arms  about  4  inches  apart.  Wire  this  to  a  board  or  clamp  it  firmly  to  a  ring  stand  in  an 
upright  position.  To  one  end  of  the  tube  attach  a  small  funnel  by  means  of  a  rubber 
connection.  Slowly  pour  in  enough  mercury  to  make  a  column  about  2  inches  high  in 
each  arm  of  the  tube.  To  the  other  end  of  the  tube  attach  a  rubber  connecter  closed 
with  a  pinch  clamp.  Measure  the  length  of  the  air  column  in  the  closed  arm  of  the  tube. 
Now  add  mercury  through  the  funnel  and  note  the  effect  upon  the  volume  of  the  air  in 
the  closed  arm.  Has  any  of  the  air  escaped  ?  How  has  it  changed  ?  When  the  open  arm 
is  nearly  filled  with  mercury,  slowly  open  the  pinch  clamp  and  listen  for  any  evidence 
which  will  help  you  to  answer  the  above  questions. 

Additional  problems.  When  an  automobile  or  bicycle  tire  is  said  to  be  full  of  air  can  more 
air  be  pumped  into  it  ? 

What  causes  the  loud  report  when  an  automobile  tire  bursts  ? 

In  a  flask  which  is  one  fourth  filled  with  water,  insert  a  rubber  stopper  through  which 
a  glass  tube  extends  almost  to  the  bottom  of  the  flask.  The  outer  end  of  the  tube  should  be 
drawn  to  a  fine  opening.  Blow  through  the  tube;  note  and  explain  what  occurs  when  you 
stop  blowing. 


fit  the  glass 

A 


!  =<K 


[25] 


EXERCISE  21 
DO  GASES  MIX  WITH  ONE  ANOTHER? 

Materials.  The  air  of  the  schoolroom ;  any  other  gas,  as  illuminating  gas  or  ammonia  gas 
escaping  from  ammonia  water. 

Directions.  With  pupils  seated  at  their  desks,  open  the  gas  jet,  noting  the  exact  time  of  doing 
so.  Allow  each  pupil  to  record  the  time  when  he  first  detects  the  illuminating  gas.  Does  the  illumi- 
nating gas  reach  all  parts  of  the  room  ?  Have  you  any  idea  as  to  how  it  passed  through  the  air  ? 
Open  the  windows,  and  after  a  few  minutes  see  if  you  can  detect  the  illuminating  gas.  What 
has  occurred  ? 

NOTE.    Ammonia  gas  may  be  used  instead  of  illuminating  gas  in  the  above  experiment. 

Additional  problems.  Is  it  a  good  plan  to  use  a  lighted  match  in  hunting  for  a  supposed  leak  in  a  gas 
pipe?  Why? 

If  sufficient  illuminating  gas  has  escaped  into  a  room  so  that  the  odor  of  the  gas  may  readily  be 
detected  in  all  parts  of  the  room,  it  is  sometimes  said,  "  The  room  is  full  of  gas."  Is  there  no  air  present  ? 


[26] 


EXERCISE  22 

WILL  GASES  MIX  WITH  ONE  ANOTHER  IF  THE  LIGHTER  GAS  IS  PLACED  ABOVE 

THE  HEAVIER  ONE? 

Materials.    Two  wide-mouthed  bottles  (about  6-  or  8-ounce  bottles);  illuminating  gas;  air. 

Directions.  Fill  a  wide-mouthed  bottle  with  illuminating  gas  by  collecting  over  water.  Close  the 
mouth  of  the  bottle  with  a  card  and  place  the  gas-filled  bottle,  mouth  downward,  upon  a  similar  bottle 
filled  with  air.  Withdraw  the  card.  The  air  and  the  illuminating  gas  will  thus  be  in  contact  in  the 
necks  of  the  bottles  with  the  lighter  of  the  two  gases  above. 

After  fifteen  or  twenty  minutes  test  each  bottle  with  a  flame  to  discover  whether  the  illumi- 
nating gas  has  gone  down  into  the  lower  bottle,  or  air  from  the  lower  bottle  has  gone  up.  How  do 
you  explain  the  results  ? 

Additional  problem.  Why  are  not  the  gases  of  the  air  in  separate  layers  ?  Would  they  be  if  there  were 
no  winds  ? 


[27] 


EXERCISE  22  A 
DO  LIQUIDS  DIFFUSE? 

Materials.  A  tall,  narrow  glass  cylinder  or  jar ;  litmus  solution ;  a  long  glass  funnel  tube ; 
sulphuric  acid. 

Directions.  Fill  the  glass  cylinder  or  jar  with  water  colored  blue  with  litmus,  to  which  a  drop 
of  ammonia  has  been  added.  Insert  a  long  glass  funnel  tube,  and  pour  into  it  two  or  three  drops  of 
sulphuric  acid.  Allow  the  jar  to  stand  undisturbed  with  the  funnel  in  position  for  a  few  days.  Since 
the  acid  is  nearly  twice  as  heavy  as  water  it  will  soon  find  its  way  to  the  bottom  of  the  jar.  The 
acid  turns  blue  litmus  to  a  red  color.  Note  whether  there  is  any  indication  that  the  heavier  acid  goes 
up  through  the  water. 

In  case  acid  and  litmus  are  not  at  hand,  fill  the  jar  with  clear  water  and  drop  into  it  several 
crystals  of  blue  vitriol.  A  heavy  blue  solution  will  be  formed  at  the  bottom.  Observe  as  above. 
This  should  be  set  up  a  week  or  more  before  you  are  ready  to  draw  conclusions. 

Additional  problem.  If  sugar  is  placed  in  coffee  or  tea  and  the  liquid  is  not  stirred  will  the  sugar 
sweeten  it  ?  Why  ? 


[28] 


EXERCISE  23 

DOES  A  LIQUID  FILL  ALL  THE  SPACE  WHICH  IT  APPEAES  TO  FILL? 

Materials.  A  glass  tube  18  inches  long  and  about  |  inch  in  diameter;  two  cork  stoppers  to 
fit  the  tube ;  alcohol. 

Directions.  Into  the  tube,  which  is  stoppered  at  one  end,  pour  water  until  it  is  half  full.  Inclin- 
ing the  tube,  carefully  and  slowly  add  enough  alcohol  to  completely  fill  the  tube.  Stopper  the  open 
end  of  the  tube  and  invert  it  several  times,  until  the  liquids  are  completely  mixed.  Now  bring  to 
original  upright  position.  Is  the  tube  now  completely  filled  with  the  liquids  ?  How  can  you  account 
for  the  decrease  in  volume  of  the  liquids  ? 


[29] 


EXERCISE  24 
WHAT  AKE  THE  PARTS  OF  A  FLAME? 

Materials.    A  wax,  tallow,  or  paraffin  candle  ;  matches. 

Directions.  Light  the  candle.  Find  and  describe  three  layers,  or  zones,  in  the  candle  flame.  The 
inner  zone  is  dark ;  the  middle  zone  is  bright ;  and  the  outer  zone  is  pale  blue  and  forms  only  a  thin 
layer  over  the  surface  of  the  flame. 

Make  a  diagram  of  a  flame  showing  the  principal  facts.  This  should  be  of  natural  size  or  larger, 
and  may  be  colored  with  crayons  or  water  colors.  Label  the  parts. 

Additional  problem.  Does  an  illuminating  gas  flame  show  the  same  parts  as  the  candle  flame  ?  Does  the 
Bunsen  flame  ?  Does  the  kerosene  flame  ? 


[30] 


EXERCISE  25 

DO  THE  PARTS  OF  THE  FLAME  DIFFER  IN  HEAT? 

Materials.    Flame  of  a  candle;  white  paper. 

Directions.  Hold  a  piece  of  white  paper  stretched  horizontally  between  the  two  hands,  and 
quickly  thrust  it  into  the  flame  in  such  a  position  that  the  center  of  the  paper  is  just  above 
the  wick.  Hold  it  there  until  the  paper  begins  to  char,  and  then  quickly  remove  it  before  it 
catches  fire. 

Examine  the  mark  which  the  flame  has  made  upon  the  paper,  and  state  your  conclusion 
regarding  the  relative  heat  of  the  inner  and  middle  zones.  Do  you  think  that  there  is  any 
burning  taking  place  in  the  inner  zone  ?  If  not  too  much  charred,  the  paper  may  be  pasted 
in  your  notebook  as  an  illustration. 

Additional  problems.  Hold  a  match  or  a  straw  across  the  flame  for  a  moment;  then  remove  and  see 
where  the  match  or  straw  is  burned. 

See  if  you  can  quickly  put  a  match  head  into  the  central  part  of  a  Bunsen  flame  and  hold  it  there 
for  a  moment  without  lighting  it. 


[31] 


EXERCISE  26 
OF  WHAT  IS  THE  CENTRAL  PAET  OF  THE  FLAME  COMPOSED? 

Materials.    Glass  tubing ;  candle  flame ;  holding  clamp  or  wire ;  matches. 

Directions.  Prepare  a  glass  tube  several  inches  in  length  by  drawing  out  one  end  so  as  to 
secure  a  small  opening.  With  a  metal  clamp  or  wire  hold  it  nearly  vertical,  with  the  large  end 
down,  and  place  the  large  end  in  the  center  of  the  candle  flame.  Bring  a  lighted  match  to  the 
tip  of  the  tube  and  observe  what  happens. 

After  completing  this  part  of  the  experiment,  remove  the  tube  from  the  flame  and  allow  it  to 
cool.  What  is  the  nature  of  the  material  which  condenses  and  hardens  on  the  inside  of  the  tube  ? 

What  are  your  conclusions,  and  the  reasons  for  them  ? 

NOTE.  This  exercise  may  be  performed  by  the  teacher  in  a  more  striking  manner  if  the  tube  used 
is  from  8  to  10  inches  long  and  ^  inch  in  diameter.  It  should  be  clamped  firmly  in  position  at  an 
inclination  of  about  45°,  and  its  whole  length  must  be  heated  by  passing  a  flame  back  and  forth  along 
the  tube  to  prevent  cooling  and  condensation  of  the  gas  before  it  reaches  the  tip  of  the  tube. 

Additional  problems.    In  the  above  experiment  why  is  it  necessary  to  keep  the  long  tube  warm  ? 
When  the  gas  which  was  discovered  at  the  center  of  the  flame  has  passed  through  the  bright  zone, 
is  it  the  same  kind  of  gas  ? 

With  an  inverted  funnel  gather  the  escaping  gas,  and  try  to  light  it. 


[32] 


EXERCISE  27 

A  PKODUCT  OF  THE  BUBKENG  CANDLE 

Materials.    A  candle  (an  alcohol  lamp  or  Bunsen  burner  may  be  used) ;  a  piece  of  metal. 

Directions.  Hold  a  cold  metallic  object  in  the  flame  or  just  above  its  tip.  Remove  the  object  in 
a  few  moments  before  it  becomes  warmed.  What,  apparently,  is  the  substance,  other  than  soot, 
which  has  collected  on  the  surface  of  the  object? 

Additional  problems.  If  an  alcohol  lamp  or  a  Bunsen  burner  is  available,  repeat  the  experiment,  using 
these  flames.  Compare  results. 

Hold  a  dry  drinking  glass  over  a  flame  to  see  if  the  same  results  are  shown. 

When  a  kerosene  lamp  is  first  lighted  what  is  the  source  of  the  water  which  collects  on  the  inside  of 
the  lamp  chimney  ? 

When  a  kettle  of  cold  water  is  placed  over  the  flame  of  a  gas  stove,  drops  of  water  often  collect  on  the 
bottom,  of  the  kettle.  Explain. 


[33] 


L 


EXERCISE  28 

IS  WATER  A  SIMPLE  SUBSTANCE,  OR  IS  IT  COMPOSED  OF  MORE  THAN  ONE 

SIMPLE  SUBSTANCE? 

Materials.  A  bottle  with  the  bottom  removed ;  a  two-holed  stopper  fitting  the  bottle,  holes  in 
the  stopper  permitting  the  passage  of  platinum  wires  or  carbons  through  them ;  copper  wire ;  three 
or  more  dry  cells  ;  sulphuric  acid ;  two  test  tubes. 

Directions.  This  experiment  is  best  performed  by  the  teacher.  It  is  most 
conveniently  done  by  the  aid  of  a  standard  electrolysis  apparatus  such  as  is 
furnished  by  the  various  laboratory  supply  firms.  If  no  such  apparatus  is  at 
hand,  the  one  shown  in  the  diagram  may  be  prepared. 

Partly  fill  the  jar  with  a  solution  made  by  adding  one  part  of  concentrated 
sulphuric  acid  to  sixty  parts  of  water.1  Fill  the  two  test  tubes  with  the  same 
solution  and  invert  them  over  the  ends  of  the  wires  without  admitting  any  air. 
Attach  to  the  free  ends  of  the  wires  a  battery  of  three  or  more  dry  cells  con- 
nected in  series,  and  observe  what  happens.  Allow  the  gases  that  are  given 
off  to  collect  in  the  test  tubes.  Note  the  relative  volumes  of  the  contents  of 
the  two  tubes.  When  the  tube  containing  the  greater  volume  of  gas  is  nearly 
full,  disconnect  the  batteries  and  remove  this  tube,  placing  a  finger  over  the 
open  end  of  the  tube  and  keeping  the  mouth  of  the  tube  downward.  Bring  a 
lighted  match  to  the  mouth  of  the  tube  and  note  the  popping  noise  and  the 
pale-blue  color  of  the  flame.  The  gas  which  was  in  this  tube  was  hydrogen. 

Remove  the  second  tube  carefully  and  test  the  collected  gas  by  thrusting 
a  glowing,  not  flaming,  pine  splinter  into  the  mouth  of  the  tube.    Observe  what  happens.    This  gas 
is  oxygen. 

Considering  that  the  amount  of  sulphuric  acid  is  not  lessened  even  if  the  current  is  allowed  to 
pass  for  a  long  time  and  therefore  cannot  be  the  source  of  either  gas  collected,  write  your  notes  and 
answer  to  the  question  of  this  exercise. 

NOTES.  If  this  experiment  is  performed  in  a  laboratory  fitted  with  a  direct-current  electric-lighting 
circuit,  the  proper  current  may  be  obtained  by  passing  it  through  one  or  more  sixteen-candle-power  lamps. 
If  more  than  one  is  used,  they  should  be  arranged  in  parallel. 

If  wire  nails  are  used  instead  of  platinum  wires  or  carbons,  it  must  be  kept  in  mind  that  the  acid  will 
probably  act  upon  the  iron,  and  the  results  will  be  less  satisfactory. 

1  Always  add  the  acid  to  the  water,  never  in  the  reverse  order. 


[34] 


EXERCISE  29 

WHAT  IS  THE  NATUKE  OF  OXYGEN  —  THE   LESS   ABUNDANT   GAS   FORMED   IN 

THE  DECOMPOSITION  OF  WATER  ? 

Materials.  Some  test  tubes ;  potassium  chlorate  ;  a  short  piece  of  glass  tubing ;  a  piece  of  rubber 
tubing ;  pine  splints ;  a  few  wide-mouthed  bottles ;  some  glass  plates  about  2  inches  square ; 
sulphur ;  iron  picture  wire ;  a  candle. 

Directions.  This  experiment  may  be  performed  by  the  teacher  or  by  the  pupils  working  in 
groups  of  two. 

Place  enough  potassium  chlorate  in  a  test  tube  to  make  a  layer  about  three  fourths  of  an  inch 
deep,  and  arrange  a  delivery  tube  to  collect  over  water 
the  gas  which  is  formed  when  the  potassium  chlorate  is 
heated.  Fill  a  test  tube  with  the  gas,  after  having  allowed 
the  gas  to  form  from  the  chlorate  long  enough  to  expel 
the  air  from  the  generator. 

a.  Note  the  odor  and  color  of  the  gas.    (The  gas  should 
first  be  washed  by  shaking  it  with  some  water  in  a  test 

tube  sealed  with  the  thumb.)    Now  take  an  ordinary  match  or  a  pine  splint  which  is  glowing,  but  not 
flaming,  and  thrust  it  into  the  tube.    Does  the  match  burn  brighter  ? 

b.  Try  to  light  the  gas  with  a  flaming  match  to  see  if  it  will  burn. 

c.  Test  the  gas  to  see  if  it  is  lighter  or  heavier  than  air  by  holding  a  glowing  splint  above  a  tube 
of  oxygen,  and  then  invert  the  tube  and  hold  the  glowing  splint  below  the  tube.   What  is  the  result  ? 

d.  Fill  a  bottle  with  the  gas,  collecting  it  over  water  as  illustrated.    Unbraid  the  end  of  a  10-inch 
length  of  ordinary  picture  wire,  heat  it  for  a  moment,  and  dip  it  into  some  'sulphur  or  paraffin. 
Ignite  the  sulphur  or  paraffin  and  thrust  it  into  the  bottle  of  gas,  and  observe  what  happens. 

e.  By  means  of  a  wire,  lower  a  short,  burning  candle  into  a  second  bottle  of  the  gas.    What 
occurs  ? 

Additional  problems.    Does  oxygen  support  combustion  of  a  piece  of  wood  better  than  air  does  ? 
Would  the  iron  of  iron-framed  buildings  be  fireproof  if  the  air  were  composed  entirely  of  oxygen  ? 
Would  it  be  of  advantage  for  the  blacksmith  to  use  oxygen  instead  of  air  in  the  bellows  to  blow  the 
fire  with  which  he  heats  his  iron  ? 


EXERCISE  30 

WHAT   IS   THE   NATURE   OF   HYDROGEN  —  THE    MORE   ABUNDANT    GAS    FORMED    IN 

THE   DECOMPOSITION   OF   WATER? 

Materials.  An  apparatus  like  that  shown  in  Fig.  36,  page  64,  of  "Elements  of  General  Science"; 
some  mossy  or  granulated  zinc ;  concentrated  hydrochloric  or  sulphuric  acid ;  test  tubes ;  wide- 
mouthed  bottles ;  pine  splints. 

Directions.  This  experiment  should  be  performed  by  the  teacher.  Since  a  mixture  of  hydrogen 
and  air  is  explosive,  a  flame  should  never  be  brought  near  the  generator  by  one  who  is  inexperienced 
in  handling  the  gas. 

Put  into  the  generator  bottle  a  small  handful  of  fragments  of  zinc  (granulated,  mossy,  or  sheet 
zinc,  or  iron).  Place  the  stopper  in  the  mouth  of  the  bottle.  Add  enough  water  through  the  funnel 
tube  to  cover  the  zinc  and  the  end  of  the  funnel  tube.  Now  add  about  10  cubic  centimeters  of  con- 
centrated hydrochloric  or  sulphuric  acid.  Observe  what  happens.  Do  not  collect  the  gas  which  first 
escapes  from  the  tube.  This  is  air  or  a  mixture  of  air  and  hydrogen.  Now  collect  two  bottles  of 
the  gas  as  in  Exercise  29 ;  cover  these  with  glass  plates  and  set  aside  for  the  tests  c  and  d  below. 
More  acid  may  be  added  if  necessary.  Also  collect  two  test  tubes  of  the  gas  for  tests  a  and  b. 

a.  Hold  a  tube  of  the  gas  mouth  downward  for  a  minute,  and  then  bring  a  flame  to  the  mouth  of 
the  tube.    What  occurs  ? 

b.  Hold  a  second  tube  of  the  gas  mouth  upward  for  one  minute,  and  then  bring  a  lighted  match 
near  the  mouth  of  the  tube.    Does  anything  happen  ?    What  do  the  results  of  a  and  b  show  relative 
to  the  weight  of  the  gas  in  comparison  with  that  of  the  air  ? 

c.  Bring  a  flame  to  the  mouth  of  a  bottle  of  the  gas  and  see  if  the  gas  burns.     Note  the  color 
of  the  flame. 

d.  Thrust  a  long  flaming  splint  into  the  second  bottle  of  the  gas,  the  bottle  having  been  inverted, 
and  note  the  result.    Does  the  gas  support  the  combustion  of  the  splint?    Hold  the  splint  in  the 
bottle  and  see  if  it  will  be  relighted  by  the  burning  gas. 

Additional  problems.    Soap  bubbles  may  be  made  by  use  of  hydrogen  gas  if  the  gas  is  first  purified  by 
being  passed  through  a  solution  of  caustic  soda. 
Why  is  hydrogen  used  in  dirigible  balloons  ? 


[381 


EXERCISE   30  A 


CAN  WATER  BE  FORMED  BY  BURNING  HYDROGEN  IN  OXYGEN? 

Materials.    Apparatus  used  in  Exercise  29,  also  that  used  in  Exercise  30  ;    clean,  dry  bottle  ;  a 
short  glass  tube  drawn  to  a  small  opening. 

Directions.    This  exercise  should  be  performed  by  the  teacher. 

Fill  a  clean  dry  bottle  with  oxygen  (see  figure).  Now  gener- 
ate hydrogen  with  the  apparatus  used  in  Exercise  30.  Insert  a 
small  glass  tube  drawn  to  a  rather  small  opening  into  the  rubber 
delivery  tube.  After  the  hydrogen  has  been  forming  for  a  few 
minutes,  catch  a  test  tube  of  the  gas  by  holding  the  tube  in  an 
inverted  position  and  bringing  the  delivery  tube  into  the  mouth 
of  the  test  tube.  Remove  the  test  tube  from  the  delivery  tube, 
and  holding  it  with  the  mouth  downward,  bring  a  lighted  match 
to  the  mouth  of  the  tube.  If  an  explosion  occurs,  catch  another 
tube  of  the  gas  and  test.  When  the  gas  is  free  from  air  and  burns 
with  a  noiseless  flame,  light  the  gas  issuing  from  the  tip  of  the  delivery  tube  and  lower  the  hydrogen 
flame  into  the  clean  bottle.  A  cover  for  the  bottle  may  be  made  by  thrusting  the  glass  tube  through 
a  piece  of  cardboard.  Allow  the  hydrogen  to  burn  until  it  is  extinguished.  What  does  the  deposit 
on  the  inside  of  the  bottle  appear  to  be  ? 

Additional  problems.    What  does  this  exercise  prove  about  the  composition  of  water  ? 
How  do  you  explain  the  formation  of  water  when  a  candle  burns  ? 


WHAT   IS   THE   GAS   GIVEN  OFF  BY   A  BURNING  CANDLE? 

Materials.  A  candle ;  a  piece  of  wire ;  a  clean  bottle ;  limewater  (prepared  by  dissolving  slaked 
lime  in  water  and  using  the  clear  water  that  may  be  poured  off). 

Directions.  Suspend  a  short  lighted  candle  by  means  of  a  wire  and  lower  it  into  a  clean  bottle  or 
glass.  Cover  the  container  as  completely  as  possible  and  observe  what  happens.  Why  does  the  can- 
dle cease  to  burn?  Now  remove  the  candle,  quickly  pour  about  10  cubic  centimeters  of  limewater 
into  the  bottle,  and,  with  a  glass  cover  on  the  bottle,  shake  the  contents  vigorously.  Observe  what 
takes  place.  Limewater  is  clouded  by  carbon  dioxide.  This  cloudiness  is  due  to  a  new  compound 
which  settles  at  the  bottom.  The  gas  which  forms  a  white  compound  with  limewater  is  called 
carbon  dioxide. 

Additional  problems.    Leave  a  wide  dish  of  limewater  exposed  for  24  hours.    What  occurs  ?    Explain. 
By  use  of  a  glass  tube  blow  your  breath  into  a  bottle  of  limewater,  and  explain  what  occurs. 
Hold  an  empty  bottle  over  a  gas  flame ;  then  pour  limewater  into  the  bottle.    Explain  results. 


EXERCISE  32 
WHAT  IS  THE  COMPOSITION  OF  CARBON  DIOXIDE? 

Materials.    Bottle  ;  oxygen  generator ;  charcoal ;  forceps ;  limewater. 

Directions.  Fill  a  bottle  with  oxygen.  Heat  a  piece  of  charcoal  (carbon)  in  a  flame,  holding  it 
with  a  forceps,  until  it  is  red-hot,  and  then  thrust  it  into  the  bottle  of  oxygen.  Observe  what  happens. 
Hold  it  in  the  bottle  until  it  no  longer  glows  and  then  remove  it.  Test  the  gas  in  the  bottle  by 
lowering  a  flaming  match  into  it.  What  do  you  think  it  is  ?  Now  add  about  10  cubic  centimeters 
of  limewater  and  shake  the  bottle.  What  does  the  result  prove  the  gas  to  be?  What  does  this 
prove  about  the  composition  of  the  gas  given  off.  by  a  candle  ?  Where  do  the  carbon  and  the  oxygen 
come  from  ? 

Additional  problems.  If  paraffin  wax  is  composed  of  carbon  and  hydrogen  only,  how  do  you  explain  the 
formation  of  carbon  dioxide  and  water  when  the  candle  burns  ? 

Why  is  the  candle  flame  hottest  in  the  thin  blue  layer  on  the  outside  of  the  flame  ? 
Why  does  not  the  gas  burn  in  the  inner  cone  of  the  flame  ? 


[42] 


EXERCISE  33 
WHAT  ARE   SOME  OF  THE  PROPERTIES   OF  CARBON  DIOXIDE? 

Materials.  Test  tubes ;  hydrochloric  acid ;  chips  of  marble ;  apparatus  used  in  Exercise  30 ; 
bottles ;  candle. 

Directions.  Generate  several  test  tubes  of  carbon  dioxide  by  the  action  of  hydrochloric  acid  on 
marble,  using  the  apparatus  shown  on  page  64  of  "Elements  of  General  Science."  This  may  be 
done  by  groups  of  students  working  together.  Test  the  gas  by  use  of  lime  water  to  see  if  it  is 
carbon  dioxide. 

a.  What  is  the  color  and  odor  of  the  gas  ?    (If  the  gas  is  not  washed  by  shaking  with  water, 
the  odor  of  hydrochloric  acid  will  be  detected.) 

b.  Is  it  lighter  or  heavier  than  air  ?    To  determine  this,  hold  a  flaming  match  over  a  bottle  of  the 
gas  and  then  invert  the  bottle  over  the  flame  of  the  match.     What  does  the  result  show  ? 

c.  Does  the  gas  burn  ?  Does  it  support  combustion  ? 

d.  Fill  a  bottle  with  carbon  dioxide.     In  another  bottle  place  a  burning  candle.     Then  pour  the 
carbon  dioxide  upon  the  candle.     Explain  results. 

Additional  problems.  Weigh  a  beaker  upon  a  balance ;  then  leave  the  exact  weights  used  upon  the  scale- 
pan.  Pour  carbon  dioxide  into  the  beaker  and  replace  the  beaker  upon  the  balance.  Explain  any  difference 
in  weight. 

Fill  a  large  container  with  carbon  dioxide ;  then  pour  the  gas  down  an  inclined  trough  which  holds 
several  very  short  burning  candles.  What  happens  ?  Why  ? 


[43] 


EXERCISE  34 
CAN  THE  GREEN  COLORING  MATTER  BE  REMOVED  FROM  LEAVES? 

Materials.  Some  fresh  green  leaves,  those  of  the  geranium  and  nasturtium ;  a  beaker  or 
metal  dish  in  which  to  boil  water ;  a  smaller  beaker  which  may  be  placed  within  the  preceding 
one ;  alcohol. 

Directions.  Since  the  common  tests  for  the  presence  of  food  materials  depend  upon  color  changes, 
it  is  necessary  to  bleach  the  leaf  before  applying  a  test  such  as  is  mentioned  in  the  following 
experiments.  It  will  often  be  better  for  the  teacher  to  perform  the  experiment,  but  the  results 
should  be  seen  and  handled  by  each  pupil. 

Dip  each  leaf  in  boiling  water  once  or  twice,  keeping  it  in  the  water  only  long  enough  to  kill  it, 
as  indicated  by  its  becoming  limp  as  if  wilted.  Place  all  the  leaves  in  a  beaker  or  other  convenient 
container  with  enough  alcohol  to  cover  them.  Heat  the  alcohol  to  about  75°  C.  for  ten  minutes. 
Since  alcohol  is  inflammable,  the  heating  is  best  accomplished  by  setting  the  vessel  containing  the 
alcohol  in  the  vessel  containing  hot  water,  using  the  principle  of  the  double  boiler. 

At  the  end  of  this  ten  minutes'  heating,  remove  the  leaves  and  rinse  in  water.  Examine  both 
leaves  and  alcohol.  What  has  happened  to  the  green  coloring  material  of  the  leaves  ?  This  coloring 
material  is  called  chlorophyll. 

NOTE.  The  experiment  can  be  performed  without  the  use  of  heat,  but  the  operation  takes  much  longer 
in  this  case.  Pupils  may  perform  the  experiment  at  home  by  immersing  leaves  in  cold  alcohol  for  24  hours 
or  longer.  In  this  case  keep  the  dish  or  bottle  tightly  closed  to  prevent  evaporation  of  alcohol. 

Wood  alcohol  has  the  same  effect  upon  the  chlorophyll  as  common  or  grain  alcohol,  but  because  of  the 
poisonous  nature  of  wood-alcohol  fumes  it  is  better  to  use  grain  alcohol. 

Additional  problems.  How  do  you  account  for  the  peculiar  appearance  of  shoots  and  leaves  of  plants 
such  as  potatoes,  asparagus,  etc.,  which  have  grown  entirely  in  darkness  ? 

Plant  mustard  seeds,  or  those  of  wheat,  oats,  and  beans,  in  darkness,  and  remove  them  to  the  light  when 
the  plants  are  an  inch  tall.  What  color  changes  follow  removal  to  the  light  ? 

Evaporate  the  alcohol  in  which  chlorophyll  was  dissolved,  evaporating  it  slowly  by  allowing  the  dish 
to  stand  in  a  draft.  What  is  left  in  the  dish  ? 


[    I!    | 


EXERCISE  35 

IS  THERE  A  FOOD  MATERIAL  IN  THE  LEAF,  AND  DOES  IT  HAVE  ANY  RELATION 

TO  CHLOROPHYLL? 

Materials.  A  fresh  white  .potato  or  some  commercial  starch ;  plants  with  white-spotted  or  par- 
tially green  leaves,  as  some  kinds  of  geraniums ;  dilute  solution  of  iodine  (tincture  of  iodine)  ;  the 
apparatus  and  materials  used  in  the  preceding  exercise. 

Directions.  Cut  a  thin  slice  from  the  potato  or  spread  out  some  commercial  starch  on  a  glass 
plate,  and  place  upon  it  a  drop  of  the  dilute  iodine  solution.  What  is  the  color  of  starch  when 
treated  with  this  solution  ? 

Select  a  number  of  leaves  which  have  been  exposed  to  the  sun  for  several  hours.  Remove  them 
from  the  plant.  Note  carefully  and  make  sketches  to  show  the  size  and  location  of  the  light  spots 
of  the  leaf.  Remove  the  chlorophyll  from  the  leaves  as  in  the  preceding  experiment. 

When  the  chlorophyll  has  been  removed  from  the  leaves,  take  them  from  the  alcohol,  place  them 
in  a  dish,  and  cover  them  with  some  of  the  dilute  iodine  solution. 

In  five  or  ten  minutes  examine  the  leaves.  What  do  the  results  show  ?  Examine  the  variegated 
leaves  to  determine  whether  there  is  any  relation  between  the  location  of  the  starch  and  the  location 
of  the  chlorophyll. 

Additional  problems.    Can  non-chlorophyll-bearing  plants  make  food  material  ? 
Do  plant  stems  contain  chlorophyll  ? 
Where  is  the  chlorophyll  in  a  cactus  plant  ? 


[46] 


EXERCISE  36 
IN   WHAT   PART  OF  THE  LEAF  IS   THE  CHLOROPHYLL  ? 

Materials.  Thin  leaves,  as  those  of  moss,  water  weed  (Elodea),  pondweed  (Potamogetori) ; 
one  or  more  compound  microscopes,  or  a  microprojection  apparatus ;  glass  slides  and  cover  glasses. 

Directions.  If  a  sufficient  number  of  compound  microscopes  are  to  be  had,  each  pupil  may  per- 
form this  experiment  independently,  but  if  there  is  only  one  microscope,  the  teacher  should  arrange 
a  demonstration  exercise.  If  the  school  possesses  a  microprojection  apparatus,  the  specimen  may  be 
shown  to  the  entire  class  at  once. 

Mount  a  very  thin  leaf  in  a  drop  of  water  on  a  glass  slide,  cover  with  the  cover  glass,  and 
examine  first  with  the  low  power  and  then  with  the  high  power  of  the  microscope. 

Does  the  chlorophyll  color  the  leaf  evenly  ?  Can  you  distinguish  the  rounded  bodies  which  are 
called  chloroplasts  ?  Is  there  any  chlorophyll  in  the  leaf  which  is  not  in  the  chloroplasts  ?  Groups 
of  these  chloroplasts  and  other  substances  are  inclosed  within  transparent,  thin  walls.  These  are 
the  cell  walls,  and  the  spaces  inclosed  by  them  contain  not  only  the  chloroplasts  but  also  the  other 
living  material  of  the  cell.  The  living  material  is  so  transparent  that  it  will  probably  not  be  seen. 

Observe  and  describe  carefully  all  that  has  been  done. 

Additional  problem.  Is  the  upper  or  lower  surface  of  ordinary  leaves  more  green  ?  Is  this  true  of 
all  leaves  ? 


[47] 


EXERCISE  37 
WHAT  IS  THE  NATURE  AND  USE  OF  THE  OUTER  COVERING  OF  THE  LEAF? 

Materials.  Some  rather  thick  leaves  (life  plant  (Bryopliyllum)  and  live-forever  are  good,  as 
are  most  species  of  lily,  iris,  and  amaryllis). 

Directions.  Peel  off  a  bit  of  the  "  skin "  (epidermis)  from  each  surface  of  the  leaf,  noting 
especially  its  thinness  and  transparency.  If  you  cannot  peel  off  the  epidermis,  try  to  scrape  away 
one  covering  and  all  the  other  material  of  the  leaf  from  a  small  area,  leaving  only  the  other 
epidermis.  Write  notes  describing  the  epidermis. 

Describe  the  kind  of  material  that  fills  the  space  between  the  upper  and  the  lower  epidermis.  It 
is  called  the  mesophyll,  meaning  "  middle  leaf."  Is  it  easily  injured  ?  Let  a  piece  of  the  leaf,  with 
epidermis  removed,  lie  on  the  desk  for  a  while,  and  note  the  effect  on  the  mesophyll. 

Explain  the  use  of  the  epidermis  with  proofs  secured  from  your  study.  See  pages  71— 74, 
"  Elements  of  General  Science,"  for  a  discussion  of  the  internal  structure  of  the  leaf. 

Additional  problems.  Examine  a  piece  of  the  epidermis,  mounted  in  water,  under  the  microscope.  Note  the 
shape  of  the  cells.  Are  they  all  of  one  kind  ?  Can  you  locate  the  crescent-shaped  cells  (guard  cells)  with 
the  slit-like  opening  between  them  ?  These,  with  the  openings,  are  the  so-called  "  breathing  pores  "  or 
stomata.  Do  the  guard  cells  have  chloroplasts  ?  Are  the  guard  cells  of  the  same  shape  in  all  stomata  ? 
in  stomata  of  different  leaves  ?  at  different  times  of  day  ? 

Study  a  cross  section  of  a  leaf. 


[48] 


EXERCISE  38 

IS  THERE  A  WASTE  PRODUCT  GIVEN  OFF  DURING  FOOD  MANUFACTURE? 

Materials.  An  aquarium  containing  some  submerged  water  plants  (the  following  may  be 
grown  in  such  aquaria:  water  weed  (ElodecC),  the  pondweeds  (Potamogeton),  water  milfoil 
(Myriopliylluni),  and  horn  wort  (Ceratophyttum),  these  being  common  in  most  parts  of  the  country). 

Directions.  Place  the  aquarium  with  submerged  water  plants  in  the  sunlight  and  examine  it 
after  fifteen  or  twenty  minutes.  Under  these  conditions  the  manufacture  of  foods  should  be  going 
on  in  the  green  parts  of  the  plants.  Observe  whether  a  gas  is  given  off  from  the  plants.  Darken 
the  aquarium  and  after  a  little  while  examine  again  to  see  whether  the  gas  is  still  coming  off  from 
the  plants. 

Almost  any  kind  of  submerged  water  plant  will  answer  for  this  experiment.  During  the  growing 
season  they  can  be  obtained  in  most  bodies  of  shallow  and  rather  quiet  water,  such  as  the  margins 
of  lakes  and  rivers.  They  grow  readily  in  aquaria.  Every  laboratory  should  carry  several  such 
aquaria  through  the  winter. 

Additional  problems.  In  drinking  troughs  for  domestic  animals  where  water  stands  for  a  long  time, 
small,  threadlike  green  plants  (the  pond  scums)  often  are  found  growing.  Observe  these  plants  when 
the  sun  is  shining  upon  them.  What  do  you  think  is  the  origin  of  the  bubbles  seen  among  these  plants 
and  arising  from  them  ?  Similar  conditions  may  be  observed  when  pond  scums  are  found  floating  at  the 
top  of  the  water  of  ponds  and  sluggish,  streams. 

Heat  water  until  the  air  in  it  has  been  driven  to  the  surface.  Cool  the  water  as  rapidly  as  possible 
until  it  is  at  air  temperature.  Place  water  plants  in  this  water  and  place  in  the  light.  Are  gas  bubbles 
thrown  off  by  the  plants  in  this  case  ?  By  means  of  a  glass  or  rubber  tube  blow  your  breath,  into  the 
water  at  the  bottom  for  a  few  minutes.  Does  this  seem  to  affect  the  quantity  of  gas  bubbles  later  produced 
by  the  plants  ? 

An  interesting  modification  of  the  experiment  of  this  exercise  is  possible  if  an  arc-light  stereopticon 
is  available.  In  this  case  a  sprig  of  one  of  these  plants  may  be  placed  in  water  in  one  of  the  thin-glass 
tanks  which  are  supplied  for  the  purpose,  and  inserted  in  place  of  the  slide.  The  light  will  be  sufficiently 
intense  to  enable  the  plant  to  carry  on  photosynthesis,  and  bubbles  will  be  seen  to  rise  from  the  plant. 


[49] 


EXERCISE  39 

WHAT   IS   THE   NATURE  OF  THE  GAS   GIVEN  OFF  DURING   CHLOROPHYLL   WORK? 

Materials.    Deep  glass  jar  or  aquarium  ;  large  glass  funnel ;  test  tube. 

Directions.  Collect  some  of  the  gas  which  arises  from  the  plants  under  the  conditions  of  Exercise 
38.  Test  it  in  the  different  ways  which  you  used  in  earlier  experiments,  to  find  out  if  it  is  one  of  the 
gases  with  which  you  are  familiar. 

The  collection  may  best  be  done  in  the  following  manner:  Put  the  plants  under  an  inverted 
glass  funnel  in  a  deep  jar.  The  funnel  must  be  wholly  submerged.  Fill  a  test  tube  with  water  and 
invert  it  over  the  stem  of  the  funnel.  The  bubbles  which  arise  from  the  plants  will  pass  up  into  the 
test  tube,  which  may  be  removed  for  the  tests  when  a  sufficient  quantity  has  been  collected.  To  col- 
lect a  sufficient  quantity  of  the  gas  within  a  reasonable  time  it  will  be  necessary  to  use  a  large 
quantity  of  plants  and  therefore  a  large  funnel. 

Additional  problems.    In  what  sense  is  it  true  that  a  green  plant  is  an  oxygen-producing  machine  ? 

Of  what  significance  is  it  to  other  living  things  to  have  large  quantities  of  oxygen  set  free  by  green  plants  ? 

Can  animals  contribute  to  the  supply  of  free  oxygen  in  the  air  ?    Can  mushrooms  and  molds  ? 


[51] 


EXERCISE  40 
HOW  DOES  A  DEPENDENT  PLANT  LIVE? 

Materials.    A  piece  of  bread  or  stale  banana ;  a  glass  dish  with  cover ;  a  magnifying  glass. 

Directions.  Moisten  a  piece  of  bread  slightly  and  expose  it  to  the  dust  of  a  room  for  an  hour ; 
then  cover  it  to  prevent  drying,  and  put  it  in  a  warm  place.  If  the  banana  is  used  it  is  treated  in  the 
same  way,  except  that  it  should  not  be  moistened.  Observe  daily.  One  or  more  varieties  of  mold  will 
appear  within  four  or  five  days.  Describe  the  growth  of  the  mold  and  its  appearance.  From  what 
source  do  you  think  it  secures  its  nourishment  ?  Do  you  think  it  manufactures  carbohydrates  ? 

Study  with  a  magnifier  or  microscope  to  learn  more  about  its  structure.  Note  particularly  the 
dustlike  spores  and  the  way  in  which  they  occur  on  the  plant.  If  satisfactory  observations  of  the 
mold  are  secured  under  magnification,  make  sketches  showing  the  structures. 

These  spores  are  the  reproductive  bodies.   How  well  are  they  adapted  for  distribution  by  the  air  ? 

Additional  problems.  Can  you  explain  how  the  mold  came  to  grow  on  the  bread  without  anyone's  pur- 
posely planting  it? 

If  bread  or  fruit  which  is  entirely  mold-free  is  kept  tightly  closed  in  a  mold-free  container,  will  mold 
develop  on  the  bread  ? 

What  other  kinds  of  plants  do  you  know  which  are  dependent  in  the  same  sense  that  mold  is  ? 

In  what  ways  is  the  life  of  rusts  and  smuts  like  that  of  mold  ?    How  different  ? 


[52] 


EXERCISE  41 
WHAT   IS   THE  NATURE   OF   THE  YEAST  PLANT? 

Materials.  Cake  of  compressed  yeast ;  molasses  or  sugar ;  bottles ;  rubber  and  glass  tubing ; 
limewater. 

Directions.  Dissolve  some  sugar  or  molasses  in  water.  Do  not  make  the  solution  stronger  than 
10  per  cent.  Add  a  little  yeast  which  has  been  thoroughly  mixed  with  water. 

From  day  to  day  note  the  bubbles  which  rise  and  the  increasing  amount  of  sediment  and  scum. 

Place  some  of  the  solution  and  sediment  in  a  bottle  and  close  the  bottle  with  a  one-holed  rubber 
stopper  through  which  a  glass  tube  has  been  passed.  Attach  a  rubber  tube  and  collect  some  of  the 
gas  which  escapes,  as  you  did  in  Exercise  29.  It  may  take  a  day  or  more  to  fill  a  bottle.  Test  the 
collected  gas  with  a  flame,  with  limewater,  and  by  any  other  means  that  you  think  of,  to  find  out 
whether  it  is  one  of  the  gases  with  which  you  are  familiar. 

When  you  have  discovered  what  gas  it  is  that  is  coming  from  the  sugar  solution,  try  to  explain 
how  it  may  have  been  produced. 

Additional  problems.    If  a  compound  microscope  is  available,  examine  the  sediment  to  see  what  the  yeast 
plant  is.    How  are  new  yeast  plants  formed  ? 
How  does  yeast  cause  bread  to  "  rise  "  ? 


[53] 


EXERCISE  42 
WHAT  EFFECT  HAS  HEAT  UPON  THE  YEAST  PLANT  AND  FEKMENTATION  ? 

Materials.    Test  tube  or  flask ;  cotton  batting ;  the  sugar  solution  used  in  the  preceding  exercise. 

Directions.  Stir  very  thoroughly  the  fermenting  sugar  solution  in  the  generator  used  in  the 
preceding  experiment,  and  pour  some  of  it  into  a  flask  or  a  test  tube.  Heat  it  to  boiling  temperature 
for  a  few  minutes,  and  then  plug  the  flask  or  tube  with  a  cotton  stopper.  Allow  the  tube  to  stand 
for  a  day,  and  observe  if  fermentation  continues.  What  is  the  effect  of  heat  upon  yeast  plants  ?  To 
what  practical  use  could  you  put  the  information  gained  in  this  exercise  ? 

Additional  problems.  How  is  it  that  cider  or  sugar  solutions  ferment  even  when  no  yeasts  have  been 
purposely  placed  in  them  ? 

Why  was  a  cotton  stopper  used  in  the  above  experiment  instead  of  a  cork  or  rubber  stopper  ?  Why 
use  any  stopper  ? 

Does  fermentation  continue  in  bread  after  the  bread  is  baked  ? 


[54] 


EXERCISE  43 


HOW  DO  BACTERIA  ACT  ON  MILK,  AND  HOW  MAY  MILK  BE  PRESERVED  FROM 

SUCH  ACTION? 

Materials.  Test  tubes ;  cotton  ;  skim  milk  ;  funnel ;  rubber  and  glass  tubing  ; 
pinch  clamp ;  wire  basket ;  formalin ;  steam  sterilizer  (may  be  made  with  common 
materials  as  directed  below)  ;  gummed  labels. 

Directions.  Pupils  should  work  in  groups  of  two.  Each  group  should  be  pro- 
vided with  six  clean,  dry  test  tubes  and  enough  cotton  to  make  plugs  for  the  tubes. 
Place  about  1  inch  of  skim  milk  in  each  test  tube.  Avoid  getting  milk  on  the 
mouth  or  upper  inner  part  of  the  tube  by  using  a  large  funnel  fitted  with  a  rubber 
connecter  with  a  pinch  clamp  ;  the  end  of  the  rubber  tube  holds  a  glass  tube  drawn 
out  to  a  small  opening.  Pour  the  milk  into  the  funnel.  The  proper  volume  of  milk 
may  be  allowed  to  enter  the  tube  by  controlling  the  pinch  clamp.  Immediately 
plug  the  test  tubes  with  cotton.  Set  one  tube  in  the  rack  and  with  a  gummed 
label  mark  it  "  1." 

Place  the  other  five  tubes  in  a  wire  basket  and  treat  as  described  below.  Place 
the  tubes  in  a  steam  sterilizer.  Sterilizers  such  as  are  often  used  for  sterilizing  milk 
for  small  children  will  be  as  satisfactory  as  the  laboratory  type.  Keep  the  water  in 


rl 


TUBE  1 

TUBE  2 

TUBE  3 

TUBE  4 

TUBE  5 

TUBE  6 

1st  day 

Sterilized 
minutes 

Sterilized 
.minutes 

Sterilized 
.    .minutes 

Sterilized 
..  .  minutes 

Sterilized 
minutes 

2d    day 

Sterilized 
minutes 

Sterilized 
minutes 

Sterilized 
minutes 

Sterilized 
minutes 

Sterilized 
minutes 

3d    day 

Sterilized 
minutes 

Sterilized  ....min. 
1  drop  sour  milk 
added 

Sterilized  ....min. 
1  drop  sour  milk 
1  drop  formalin 

Sterilized  ....min. 
10   drops    drink- 
ing water  added 

Sterilized  ....min. 
Plug  removed 
30  minutes 

4th  day 

5th  day 

(>th  day 

7th  day 

8th  day 

9th  day 

10th  day 

[00] 


EXERCISE  43  (Continued) 

the  sterilizer  boiling  for  twenty  minutes.  Allow  the  tubes  to  cool,  repeat  the  treatment  twenty-four 
hours  later,  and  preferably  a  third  time  one  day  later.  If  no  sterilizer  is  to  be  had,  set  the  tubes  in 
a  vessel  of  water  in  such  position  that  they  are  half  immersed  in  the  water  but  are  not  in  contact 
with  the  bottom  of  the  vessel.  Boil  as  directed  above. 

It  is  supposed  that  the  heating  will  have  killed  any  living  things  in  the  tubes,  as  in  Exercise  42. 
The  three  sterilizations  are  intended  to  make  sure  of  this.  Set  aside  one  of  the  sterilized  tubes  to  see 
whether  any  changes  will  occur  in  it.  Label  it  "  2."  Do  not  at  any  time  during  the  experiment 
remove  the  cotton  plug.  Label  the  remaining  tubes  "  3,"  "  4,"  "  5,"  "  6." 

When  tubes  "  3  "  to  "  6  "  have  cooled  from  the  last  sterilization,  treat  them  as  indicated  in  the 
tabulation  above.  Keep  a  daily  record  of  observations  for  at  least  a  week.  Curdling,  becoming 
watery,  and  alterations  of  color  are  changes  which  are  easily  seen. 

Make  each  tube  the  basis  of  a  statement  regarding  what  you  have  learned  from  it.  Your  notes 
should  include,  in  addition  to  the  statement  of  the  method  of  preparing  and  sterilizing  the  tubes  and 
a  statement  of  the  conclusions,  a  tabular  presentation  of  the  records  of  the  experiments. 

Additional  problems.    Is  there  objection  to  the  use  of  formalin  in  preserving  milk  ? 

Why  is  absolute  cleanliness  necessary  in  handling  milk  ?    How  can  such  cleanliness  be  secured  ? 

What  is  the  importance  to  the  public  of  having  great  care  observed  in  handling  milk  ? 

When  canning  fruit,  should  the  fruit  be  allowed  to  cool  before  the  lids  are  placed  on  the  cans  ?    Why  ? 


[56] 


EXERCISE    44 
WHAT   CHANGES   IN  VOLUME   TAKE  PLACE   WHEN  WATER  FREEZES? 

Materials.    A  short  test  tube  or  a  small  vial  without  a  constricted  neck  ;  a  two-holed  rubber 
stopper  to  fit  the  test  tube  or  vial ;   a  thermometer ;   a  glass  tube  about  one  foot  in  length 
and  fitting  tightly  one  of  the  holes  in  the  stopper ;  ice  or  snow ;  salt.  ~ 

Directions.  Fill  the  test  tube  or  vial  with  water  and  close  it  with  a  two-holed  rubber 
stopper  in  which  are  a  glass  tube  and  a  thermometer.  The  tube  should  not  extend  below  the 
lower  surface  of  the  stopper.  Push  the  stopper  down  until  the  glass  tube  is  about  half  full  of 
water.  Fasten  on  the  back  of  the  glass  tube  a  paper  centimeter  scale  cut  from  cross-section 
paper. 

Set  the  test  tube  or  vial  in  a  beaker  or  cup  and  surround  it  with  a  freezing  mixture 
made  by  adding  ice  or  snow  to  a  heavy  brine  solution. 

Watch  the  tube  from  the  beginning,  and  record  the  changes  in  height  of  water  in  the  tube. 
Note  the  height  of  the  column  for  each  degree  of  change  of  temperature,  and  record  each 
measurement  with  the  reading  of  the  thermometer  at  the  same  time. 

After  you  have  recorded  your  observations,  try  to  make  conclusions,  with  proof,  on  the 
following  points :  What  changes  in  volume  take  place  when  water  freezes  ?  At  what  tempera- 
ture does  a  given  amount  of  water  occupy  the  least  volume  ?  When  is  water  heaviest  per 
cubic  inch  ?  When  lightest  ?  Compare  your  results  with  results'  known  to  be  correct,  which 
will  be  given  by  the  teacher  or  in  the  textbook. 

Additional  problems.    Why  does  ice  float  ? 

Why  do  water  pipes  burst  when  the  water  within  freezes  ? 


EXERCISE  45 

WHAT  HAPPENS   WHEN  WATER  BOILS,  AND  AT  WHAT  TEMPERATURE  DOES 

THIS  TAKE  PLACE? 

Materials.  A  flask ;  a  two-holed  rubber  stopper  to  fit ;  a  thermometer ;  a  glass  tube ;  a  ring 
stand  with  clamps  (or  other  support). 

Directions.  Set  up  an  apparatus  as  shown  in  the  diagram.  The  flask  should  be  about  one  half 
full  of  water  into  which  has  been  dropped  a  few  grains  of  sawdust  or  very  small  bits  of  porous 
paper.  Note  the  temperature  of  the  water,  and  then  heat  gently.  Small  bubbles  will  soon  appear  on 
the  walls  of  the  vessel,  or  rise  through  the  water.  Note  the  temperature  when  bubbles  first 
appear.  What  are  these  bubbles  ?  (Set  a  glass  of  cold  water  in  the  sun  or  near  the  radia- 
tor, and  see  if  the  same  thing  happens.)  While  heating,  observe  the  movement  of  the 
particles  and  explain  why  they  move  as  they  do.  When  the  temperature  is  near  100°C. 
or  212°F.,  note  the  large  bubbles  which  form  at  the  bottom  of  the  flask.  What  are  these  ? 
Do  they  change  in  size  as  they  rise  through  the  water  ?  What  causes  some  to  disappear 
completely  ?  When  the  water  is  boiling  vigorously,  note  its  temperature.  W7hat  occu- 
pies the  space  above  the  water  in  the  flask  ?  Allow  it  to  boil  for  ten  minutes,  and  then 
compare  the  volume  left  with  the  original  volume.  How  do  you  explain  the  difference  ? 
What  do  you  understand  by  the  statement  that  water  boils  at  about  100°C.  or  212°F.  ? 

Additional  problems.    What  differences  are  there  between  ordinary  water  and  steam  ? 

Boil  a  half  flask  of  water  and,  when  at  boiling  temperature,  remove  the  flame  and  stopper  the  bottle 
air-tight  with  a  rubber  stopper.  Allow  the  flask  and  water  to  cool  for  five  or  ten  minutes ;  then  invert 
the  flask  and  pour  cold  water  on  it.  Explain  what  happens. 


[60] 


EXERCISE  46 

HOW  IS  WATER  DISTILLED,  AND  HOW  MAY  DISSOLVED   SOLIDS  BE  SEPARATED 

FROM  WATER? 

Materials.  Apparatus  of  the  preceding  exercise ;  a  bent  glass 
tube ;  test  tube  ;  beaker  or  cup ;  salt. 

Directions.  Place  about  100  cubic  centimeters  of  water  in  a  flask 
and  add  3  or  4  teaspoonfuls  of  salt.  Shake  it  to  hasten  solution.  Taste 
the  solution.  Now  connect  a  delivery  tube  as  shown  in  the  diagram, 
and  heat  the  solution  to  boiling.  Keep  the  water  in  the  beaker  cold 
by  adding  ice  or  snow.  Observe  what  happens.  After  five  minutes  of 
boiling  remove  the  beaker  and  test  tube,  also  the  burner.  Taste  the 
liquid  that  has  distilled  over  into  the  receiver.  This  is  called  the 
distillate.  Is  any  salt  present? 

Additional  problems.  Put  ink  or  other  colored  liquid  in  a  flask  of  water. 
Determine  whether  the  coloring  material  is  present  in  the  distillate. 
How  could  you  obtain  fresh  water  from  salt  water  or  sea  water  ? 
Of  what  commercial  use  is  the  process  of  distillation  ? 


[62] 


EXERCISE  47 
WHAT  EFFECT  HAS    EVAPORATION  UPON   TEMPERATURE? 

Materials.    A  thermometer ;  cotton ;  alcohol ;  a  small  cup  or  drinking  glass. 

Directions.  Record  the  temperature  of  the  room.  Twist  a  small  piece  of  cotton  about  the  bulb 
of  a  thermometer.  This  may  be  fastened  on  with  a  rubber  band.  Place  the  bulb  in  water  which 
has  stood  until  it  is  at  about  the  room  temperature.  Record  the  exact  temperature  of  the  liquid. 

Remove  the  bulb  from  the  water.  Watch  the  thermometer  carefully,  noticing  and  recording  any 
temperature  changes  until  no  further  changes  occur.  How  do  you  account  for  the  temperature 
changes  which  you  have  noted  ? 

Wet  the  bulb  of  the  thermometer  again  and  fan  it.  How  does  its  temperature  change  ?  Why  ? 
How  does  the  temperature  change  when  the  bulb  of  the  thermometer  becomes  dry  ?  Repeat  the 
experiment  with  the  same  thermometer  and  the  same  cotton  covering,  using  alcohol  instead  of 
water.  Explain  the  difference  in  results. 

In  your  conclusions  state  what  you  have  learned  regarding  the  effect  of  evaporation  and  the 
rate  of  evaporation. 

Additional  problems.  Put  a  drop  or  two  of  ether  on  the  back  of  your  hand  and  explain  the  sensation 
produced. 

What  are  the  principles  underlying  the  use  of  ammonia  in  ice  making  ? 

Why  do  people  fan  themselves  during  hot  weather  ? 

When  bathing  in  water  which  is  cooler  than  the  atmosphere,  one  may  feel  comfortably  warm  in  the 
water  but  unpleasantly  cool  when  out  of  the  water.  How  may  this  fact  be  explained  ? 


[63] 


EXERCISE  48 
HOW  RAPIDLY  DOES  WATER  EVAPORATE  IN  THE  CLASSROOM? 

Materials.    A  cup  or  beaker ;  a  pair  of  balances  with  metric  weights. 

Directions.  Fill  a  cup  or  beaker  with  water  to  within  half  an  inch  of  the  top.  Weigh  it  and  set 
it  aside  in  an  exposed  place.  Note  the  time  when  it  was  weighed. 

On  the  next  day  or  some  succeeding  day  at  the  same  time  weigh  again.  How  much  evaporated 
during  each  24-hour  period?  Secure  the  diameter  of  the  cup  in  centimeters  or  millimeters,  and 
calculate  what  depth  of  water  evaporated  from  the  cup.  (One  cubic  centimeter,  or  1000  cubic 
millimeters,  weigh  one  gram.) 

Additional  problems.  Assuming  that  evaporation  would  continue  at  the  rate  shown  in  the  above 
experiment,  what  depth  of  water  would  evaporate  in  one  year  ? 

Perform  the  experiment  of  this  exercise  in  the  outdoor  air,  make  calculations  for  the  yearly  evapo- 
ration as  above,  and  compare  the  results  with  those  secured  from  the  schoolroom.  Does  this  help  to 
explain  why  one's  nasal  membranes  become  extremely  dry  during  schooltime  ? 


[64] 


EXERCISE  48  A 
DOES  ICE  EVAPORATE? 

Materials.    Metal  cup  ;  balances. 

Directions.  If  Exercise  48  is  performed  during  the  winter,  this  exercise  will  be  of  much  interest 
and  can  be  done  at  the  same  time.  Put  water  in  a  tin  cup  and  set  it  outside  to  freeze.  When  the 
water  is  completely  changed  to  ice,  weigh  it  quickly  and  again  set  outside,  so  that  it  will  remain 
frozen.  On  the  next  day  and  several  following  days  weigh  it  again  and  record  the  results.  What 
conclusion  do  you  draw  ? 

Additional  problems.    Why  will  wet  clothes  dry  even  if  they  are  exposed  to  freezing  weather  ? 
What  is  the  explanation  of  the  fact  that  snow  disappears  during  a  period  of  days  when  the  temperature 
is  constantly  at  or  below  freezing  ? 


[651 


EXERCISE  49 
HOW  KAPIDLY  DOES  WATEK  EVAPORATE  FHOM  A  PLANT? 

Materials.  A  potted  plant ;  a  sheet  of  thin  rubber  (dentist's  rubber)  large  enough  to  inclose  the 
pot  in  which  the  plant  grows  ;  balances. 

Directions.  The  plant  should  be  well  watered  and  then  wrapped  in  such  manner  that  water 
cannot  evaporate  from  the  soil  or  pot.  To  do  this,  wrap  the  pot  in  a  sheet  of  thin  rubber  and 
tie  so  as  to  hold  the  rubber  closely  around  the  stem.  This  can  be  done  more  securely  if  the  plant 
selected  has  but  a  single  stem. 

Weigh  the  pot  and  the  plant  after  wrapping.  Set  it  in  a  light  place  and  weigh  again  from  time 
to  time  —  hourly,  if  possible.  Record  your  weights  in  the  table  below. 

What  does  a  loss  of  weight  indicate  ?  Can  you  account  for  any  changes  in  rate  of  evaporation  ? 
What  are  the  reasons  for  wrapping  the  pot  with  rubber  ? 


DATE 


TIME 


Loss  PER  HOUR 


Additional  problems.  Water  sometimes  evaporates  more  rapidly  from  a  vegetated  area  than  from  a 
similar  area  of  free  water.  Explain  this  fact. 

Why  must  house  plants  be  watered  more  abundantly  on  dry,  hot  days  than  on  cloudy  days  ? 

Determine  the  area  of  the  leaves  used  in  the  above  exercise  and  calculate  the  daily  evaporation  per 
square  centimeter  (evaporation  occurs  usually  from  the  lower  surface  only). 


[66] 


EXERCISE   49  A 
DOES  WATER  EVAPOEATE  FROM  A  PLANT? 

Materials.  A  large,  wide-mouthed  bottle ;  some  fresh  leaves  or  a  short,  leafy  branch ;  materials 
arranged  as  in  Fig.  62  of  the  "  Elements  of  General  Science." 

Directions.  If  it  is  not  desired  to  measure  evaporation  from  a  plant  as  in  the  preceding  exercises, 
a  simpler  experiment  may  be  used.  Inclose  several  leaves  (or  a  short,  leafy  branch)  in  a  bottle  without 
removing  them  from  the  plant.  Close  the  mouth  of  the  bottle  with  a  split  cork  stopper,  through 
which  the  branch  or  petioles  pass,  or  plug  the  opening  with  cotton.  Support  the  bottle  in  any 
convenient  way  and  set  the  whole  apparatus  in  a  light  place. 

In  about  half  an  hour  examine  the  bottle  and  explain  the  results. 


[68] 


EXERCISE  50 

HOW  DOES  A  SIPHON  WORK? 

Materials.  Rubber  tube  about  18  inches  long;  two  jars  or  pans,  one  of  which  will  hold  1  or 
2  gallons  of  water. 

Directions.  Two  students  should  work  together.  Submerge  the  rubber  tube  in  a  jar  of  water 
so  that  the  tube  will  be  filled  completely.  Close  one  end  by  pinching  and  withdraw  that  end  from 
the  water,  placing  it  in  an  empty  jar  with  the  end  of  the  tube  on  the  bottom  of  the  empty  jar. 
Release  the  tube,  observe,  and  explain  what  happens.  Allow  the  tube  to  remain  until  the  water 
stops  running.  Compare  the  depth  of  the  water  in  the  two  jars.  What  caused  the  water  to  run? 
What  caused  the  water  to  stop  running?  Write  complete  notes  on  what  you  did  and  observed, 
and  an  explanation  of  the  working  of  a  siphon. 

Additional  problems.  Why  will  a  siphon  fail  to  work  if  any  part  of  the  siphon  tube  is  over  33  feet 
higher  than  the  level  of  the  water  which  is  being  siphoned  ? 

How  can  you  remove  the  stale  water  from  a  goldfish  jar  and  introduce  fresh  water  without  in  any  way 
disturbing  the  jar  ? 

A  jar  of  clear  liquid  has  a  scum  on  its  top.  How  can  you  remove  almost  all  of  the  liquid  with  the  least 
disturbance  to  the  scum  ?  How  can  you  start  the  siphon  without  submerging  the  entire  tube  in  the  liquid  ? 


[69] 


No. 
two 


16   in 
corks 


EXERCISE  51 
HOW  DOES  A  LIFT  PUMP  WORK  ? 

Materials.    A  glass  model  of  a  lift  pump   or  the  following  materials:    some  wire 
size;  glass  tubing  from  1  to  2  inches  in  diameter  and  from  12  to  18  inches  in  length; 
large  enough  to  fit  the  tubing  tightly ;  a  piece  of  thin  shoe  leather  or  harness  leather ; 
tacks  and  shingle  nails ;  a  glass  jar  or  pan. 

Directions.    This  exercise  is  best  demonstrated  by  a  model  lift  pump. 

If  such  a  demonstration  apparatus  cannot  be  had,  a  crude  one  such  as  is  shown  in 
the  diagram  may  be  constructed  by  the  teacher  or  students.  Secure  a  glass  tube  from 
1  to  2  inches  in  diameter  and  from  12  to  18  inches  long.  Cut  two  flat  corks  to  fit 
the  tube  rather  snugly.  Bore  a  small  hole  through  the  center  of  each  cork ;  then  place 
a  small,  square  piece  of  rather  heavy  sheet  rubber  or  soft  leather  over  the  hole,  and 
tack  the  piece  along  one  of  its  edges.  These  pieces  of  rubber  or  leather  will  act  as 
valves.  Place  one  cork  in  the  bottom  of  the  tube,  as  in  the  diagram.  A  few  small  nails 
driven  into  the  cork  will  keep  the  pump  from  the  bottom  of  the  jar  when  the  pump 
is  operated. 

Cut  three  lengths  of  No.  16  ordinary  iron  wire  10  inches  longer  than  the  glass 
tube.  Thrust  these  wires  through  the  cork  and  clinch  them  below  the  cork,  as  shown 
in  the  diagram.  Bend  them  above  the  cork  as  shown,  and  then  twist  the  wires  together 
to  form  a  piston  rod,  making  a  circular  handle  above.  Soak  the  valves  well ;  place  the 
piston  in  position  and  force  it  down,  observing  the  position  of  the  valves.  Now  raise  it 
and  observe  what  occurs.  Again  push  downward  and  observe.  Repeat,  and  see  if  the 
valves  work  in  the  same  way  as  above.  Why  does  the  water  rise  in  the  tube  during 
an  upstroke  ?  Write  an  explanation  of  the  working  of  a  lift  pump,  and  make  drawings 
to  show  the  principal  features. 

Additional  problems.  How  can  a  lift  pump  be  made  to  lift  water  from  a  well  more  than  33  feet  below 
the  surface  ? 

Why  must  a  pump  be  "  primed  "  ?  Why  does  water  flow  from  the  spout  only  on  the  upstroke  of  the 
lift  pump  ? 

How  does  a  force  pump  differ  from  a  lift  pump  ? 


[70] 


EXERCISE  51 A 
HOW  DOES  A  PUMP  OPERATE? 

Materials.    An  ordinary  pump  (cistern  or  pitcher  pump). 

Directions.  Operate  the  pump  slowly,  observing  all  the  facts  about  the  flow  of  the  water.  If 
possible,  take  the  pump  to  pieces  sufficiently  to  find  the  plunger,  its  valve,  and  the  valve  at  the 
bottom  of  the  cylinder.  Move  the  plunger  up  and  down  in  a  bucket  of  water  and  watch  the  action 
of  the  valve. 

When  thoroughly  familiar  with  the  pump,  make  a  diagram  showing  all  the  important  parts  and 
write  a  description  of  the  pump  and  of  the  way  it  works. 


[72] 


EXERCISE  52 

IS  THE  LATERAL  PRESSURE  IN  WATER  DIFFERENT  FROM  THE  PRESSURE 

DOWNWARD  OR  UPWARD? 

Materials.    Thin  sheet  rubber  (dentist's  rubber)  ;   a  thistle  tube ;   rubber  and  glass  tubing ;   a 
funnel ;  a  meter  (or  yard)  stick. 

Directions.  Fasten  a  thin  sheet  of  rubber  over  the  end  of  a  thistle 
tube  or  funnel.  Prepare  an  indicator,  which  consists  of  a  small  glass 
tube  bent  as  shown  and  tied  or  wired  to  a  meter  (or  yard)  stick,  the 
tubing  containing  some  ink  or  colored  water.  With  a  long  rubber  hose 
connect  the  thistle  tube  with  the  indicator.  Lower  the  thistle  tube  to  a 
certain  marked  depth  with  the  rubber  facing  upward.  Watch  the  change 
in  level  of  the  liquid  in  the  long  arm  of  the  indicator  tube.  What  does 
this  change  mean  ?  With  the  rubber  face  of  the  thistle  tube  at  the 
marked  depth  take  the  readings  on  the  indicator.  Change  the  position 
of  the  thistle  tube  so  that  the  rubber  faces  sidewise,  with  its  center  at 
the  same  depth  as  before.  Take  readings  again,  and  record.  Place  the 
thistle  tube  with  the  rubber  facing  downward,  its  center  at  the  same 
depth,  and  again  record  the  readings.  What  changes,  if  any,  are  noted 
in  the  level  of  the  liquid  in  these  three  different  positions  ?  Upon  what 
does  the  pressure  in  water  depend  ?  Would  the  readings  be  different  if 
you  placed  the  funnel  in  a  larger  jar  at  the  same  depth  ?  Try  it. 

Additional  problems.    Why  is  a  dam  built  wider  at  the  bottom  than  at  the  top  ? 
Does  the  size  of  a  reservoir  govern  the  pressure  ? 


[73] 


EXERCISE  53 

HOW  CAN  WATER  BE  USED   IN  FINDING  THE  VOLUME  OF  AN  IRREGULAR  SOLID? 

Materials.    A  graduated  cylinder ;  an  irregularly  shaped  stone ;  a  small  cord  or  wire. 

Directions.  Fill  a  graduated  (metric)  cylinder  about  half  full  of  water  and  read  accurately  the 
volume  of  water.  Suspend  a  small  stone  by  means  of  a  thread  or  fine  wire  and  lower  it  into  the 
water.  Again  take  the  reading,  and  record.  What  is  the  volume  of  the  stone  in  cubic  centimeters  ? 

Additional  problems.  Test  the  accuracy  of  the  above  experiment  by  use  of  objects  of  regular  form 
which  may  be  measured  both  as  directed  above  and  by  linear  metric  measurements. 

Determine  the  approximate  volume  of  a  large,  irregular  body  as  follows  :  Place  a  glass  dish  in  a 
larger  dish  or  jar.  Completely  fill  the  inner  dish  with  water,  but  do  not  allow  it  to  overflow.  Slowly 
lower  the  body  to  be  measured  into  the  water,  making  certain  that  all  overflow  water  is  caught  in  the 
outer  jar.  Measure  the  overflow  water  in  a  graduated  cylinder.  What  is  the  approximate  volume  of 
the  object  ?  What  are  the  sources  of  error  in  this  method  of  measurement  ? 


[75] 


EXERCISE  54 
WHAT  IS  THE  LIFTING  EFFECT  OF  WATEK  UPON  AN  OBJECT  IMMEKSED  IN  IT? 

Materials.  The  stone  used  in  the  preceding  exercise ;  balance ;  cup  large  enough  to  contain  the 
stone ;  small  cord. 

Directions.  Dry  the  stone  and  weigh  it.  Suspend  it  from  a  balance  by  a  thread  in  such  a  manner 
that  the  stone  is  immersed  in  water  but  does  not  touch  the  side  or  bottom  of  the  vessel.  Weigh 
while  in  water.  Fill  out  the  following  table : 


Weight  of  stone  in  air 

Weight  of  stone  in  water 

Loss  of  weight  in  water 

Weight  of  water  displaced 

Volume  of  water  displaced  (1  cc.  =  1  g.)         

Volume  of  stone 

Weight  of  one  cubic  centimeter  of  stone 

Stone  is  how  many  times  heavier  than  equal  volume  of  water 


Study  this  table  and  make  a  short,  clear  statement  of  the  important  facts  you  discover. 

Additional  problems.  Is  the  method  of  determining  volume  as  given  in  this  experiment  more  or  less 
accurate  than  that  of  the  preceding  experiment  ? 

If  the  density  of  an  object  is  the  weight  of  a  unit  volume  of  the  object,  what  is  the  density  of  the 
stone  used  in  the  above  experiment  ? 

It  has  often  been  noticed  that,  when  bathing,  one  can  lift  a  large  stone  from  the  bottom  to  the  top 
of  the  water,  but  cannot  lift  it  above  the  surface.  Why  is  this  ? 


[76] 


EXERCISE   55 
WHY  DO  OBJECTS  FLOAT  IN  WATER? 

Materials.    A  shallow  tin  or  granite  pan ;    a  galvanized  iron  pail ;  small  piece  of  glass  tubing ; 
paraffin  or  sealing  wax  ;  beaker ;  dry  sand ;  balance. 

Directions.  Punch  a  small  hole  in  the  side  of  the  pail 
2  or  3  inches  from  the  top.  Fit  into  the  hole  a  piece  of 
glass  tubing  2  or  3  inches  long,  and  seal  water-tight  where 
the  tube  passes  through  the  hole  in  the  pail.  Fill  the  pail 
with  water  until  water  flows  through  the  tube.  Weigh  and 
record  the  weight  of  the  pan  and  beaker.  When  the  water 
stops  flowing,  place  the  beaker  under  the  tube  ready  to 
catch  water  which  may  flow  later.  Carefully  lower  the 

pan,  allowing  it  to  rest  upon  the  water  in  the  pail.  Weigh  and  record  the  weight  of  the  water  which 
now  flows  into  the  beaker.  Add  a  weighed  quantity  of  sand  and  weigh  the  water  which  overflows. 
What  is  the  relation  between  the  weight  of  a  floating  object  and  the  weight  of  the  water  it  displaces  ? 


Additional  problem.    Why  will  not  a  cast-iron  kettle  float  ? 
meant  by  the  "  displacement "  of  a  ship  ? 


Why  does  an  iron  ship  float  ?    WThat  is 


[78] 


EXERCISE  56 

WHAT   EFFECT  DOES  LAKE  MICHIGAN  HAVE  UPON   THE  TEMPERATURE  OF 

PLACES  NEAR  IT? 

Materials.  Cross-section  paper;  the  data  given  on  pages  138  and  142,  "Elements  of  General 
Science." 

Directions.  Note  the  relative  location  of  Madison  (Wisconsin),  Milwaukee  (Wisconsin),  and 
Grand  Haven  (Michigan)  as  shown  on  the  map,  p.  142  in  the  text,  in  order  to  understand  why 
they  are  appropriate  places  for  this  study. 

Compare  first  the  figures  given  in  the  table  for  the  coldest  month  (January)  and  for  the  warmest 
month  (July).  Which  city  is  warmest  in  winter  ?  Which  is  coldest  ?  Which  is  hottest  and  which 
coolest  in  summer  ?  Which  place,  therefore,  has  the  greatest  extremes  and  which  is  most  equable  ? 
Study  the  data  for  the  other  ten  months  also,  and  find  for  yourself  the  answer  to  each  of  the 
following  questions: 

a.  How  are  the  average  winter  temperatures  of  the  three  places  related  (that  is,  which  is  highest, 
intermediate,  and  lowest)  ? 

b.  How  are  the  temperatures  related  in  summer  ? 

c.  What  is  the  difference  between  summer  and  winter  temperatures  at  Grand   Haven  ?     at 
Madison  ? 

d.  Could  Lake  Michigan  be  responsible  for  this  difference  ? 

e.  Write  a  statement  of  what  appear  to  be  the  effects  of  the  lake  on  temperature. 
Your  notes  should  include  a  clear  statement  of  the  subject  matter  of  each  question. 

If  the  school  is  located  near  a  large  body  of  water,  local  data  should  be  used  in  this  exercise 
instead  of  those  cited  above. 

The  temperature  relations  discussed  above  will  be  seen  more  clearly  if  they  are  represented 
graphically.  To  do  this,  use  a  piece  of  paper  which  has  been  prepared  as  follows:  On  a  piece  of 
cross-section  paper  number  the  horizontal  lines  to  correspond  with  the  graduation  of  a  Fahrenheit 
thermometer  scale,  placing  the  figures  in  the  left-hand  margin.  Label  twelve  of  the  heavy  vertical 
lines  with  the  names  of  the  months.  Secure  from  the  table  the  mean  temperature  for  January  at 
Madison  (16.9°).  Place  a  dot  on  the  January  line  at  a  height  to  correspond  with  16.9°  on  the 
thermometer  scale  at  the  left.  In  like  manner  represent  the  temperature  at  Madison  for  each  of 
the  twelve  months.  Connect  these  dots  with  a  continuous  line.  Do  the  same  for  Milwaukee  and 
for  Grand  Haven,  using  a  different  color  for  each. 

Additional  problem.  Compare  the  temperatures  at  a  given  point  in  California,  and  at  points  in  approxi- 
mately the  same  latitude  in  the  Rocky  Mountain  region,  Central  States  region,  and  Atlantic  Coast  region. 


f80] 


EXERCISE  56 


100°  F. 


9O     -TT 


ao 


7O 


60 


50 


40 


3O 


20 


EXERCISE  57 

WHAT  IS  THE  EFFECT  OF  LAKE  MICHIGAN  UPON  THE  SURROUNDING  COUNTRY 

DURING  COLD  WINTER  WEATHER? 

Materials.    Data  from  pages  143  and  144  in  "  Elements  of  General  Science." 

Directions.  Study  the  curves  on  page  143  of  the  textbook  for  evidences  of  the  effect  of  the  lake 
upon  temperatures.  Also  study  the  table  on  page  144,  which  shows  temperatures  during  a  cold  wave 
a  year  later.  See  whether  the  conclusions  regarding  the  effect  of  the  lake  arrived  at  by  a  study  of 
the  cold  wave  of  1912  (p.  143)  will  hold  good  for  the  cold  wave  of  1913  (p.  144). 

So  far  as  can  be  determined  from  these  two  studies,  what  is  the  effect  of  the  lake  upon  cold 
waves  ? 

Additional  problems.  Why  are  there  so  many  productive  peach  orchards  on  the  east  shore  of  Lake 
Michigan  and  few  or  none  on  the  west  shore  ? 

How  can  you  account  for  the  fact  that  there  are  large  productive  peach  orchards  about  St.  Louis  and 
in  southern  Illinois  and  few  good  peach  orchards  in  central  and  northern  Illinois  ? 


[81] 


EXERCISE  58 

IS  THERE  A  DIFFERENCE  IN  THE  RATES  AT  WHICH   SOIL  AND  WATER 

CHANGE  IN  TEMPERATURE? 

Materials.  Bunsen  burners  or  alcohol  lamps ;  metal  cups  or  pans  (not  soldered)  ;  soil ;  water ; 
thermometers. 

Directions.  Arrange  two  Bunsen  flames,  or  alcohol-lamp  flames,  to  burn  as  nearly  alike  as  pos- 
sible. Place  about  100-200  grams  of  dry  soil  in  a  cup  and  an  equal  weight  of  water  in  a  second 
cup.  Take  the  temperatures  of  both  and  leave  a  thermometer  in  each;  then  place  them  over  the 
burners  at  the  same  time.  When  one  reaches  about  100°  C.  or  21 2°  F.,  note  the  temperature  of 
the  other  and  record  both.  Which  heats  more  rapidly? 

Additional  problems.  If  a  5-pound  piece  of  iron  at  100°  C.  be  dropped  into  a  vessel  containing  5  pounds 
of  water  at  0°  C.,  the  water  will  be  warmed  and  the  iron  cooled.  What  is  the  temperature  at  which  the 
water  is  no  longer  heated  by  the  iron  ? 

On  the  beach  at  noon  of  a  bright  summer  day,  is  the  sand  of  the  beach  or  the  water  warmer  ?  Do 
the  same  temperature  relations  exist  at  midnight?  In  the  beginning  of  winter  weather  does  the  sand 
along  the  shore  or  the  water  freeze  first  ? 

Which  heats  more  rapidly  upon  a  stove,  a  kettle  of  water  or  an  iron  of  equal  weight  ? 


[82] 


EXERCISE   59 
WHAT  ARE  THE  PRINCIPAL  CHARACTERISTICS  OF  HARBORS  AND  WATERWAYS? 

Materials.    Maps  or  charts  of  waterways  or  ports. 

Directions.    Base   this   study  upon   maps   or   charts   of  the  nearest  port  or  waterwaj^  through 
which  the  commerce  of  the  local  community  passes.    Excellent  charts  of  navigable  waters  may  be 
obtained  at  nominal  cost  from  the  proper  government  authorities.     Lists  and  prices  of  such  charts 
may  be  secured  free  as  follows : 
Coasts  of  United  States 

United  States  Coast  and  Geodetic  Survey,  Washington,  D.C. 
Great  Lakes 

United  States  Lake  Survey  Office,  Detroit,  Michigan. 
Mississippi  River 

Mississippi  River  Commission,  St.  Louis,  Missouri. 

On  such  charts  note  depths,  obstructions,  channels,  lights  and  lighthouses,  buoys,  fog  signals, 
wharves,  and  other  facilities  for  safety  and  for  loading  and  unloading.  The  conditions  vary  so 
greatly  that  it  must  be  left  to  the  teacher  to  direct  the  detailed  work.  If  the  school  is  very  remote 
from  water  transportation,  the  exercise  may  be  omitted. 

Additional  problem.  With,  a  leading  product  as  a  basis  for  discussion,  as  cotton,  wheat,  coal,  iron,  or 
lumber,  indicate  the  points  to  which  the  major  part  of  the  output  is  shipped  and  the  chief  routes  of  ship- 
ment, and  thus  show  the  extent  to  which  water  enters  into  the  transportation  of  this  product. 


[83] 


EXERCISE  60 
WHAT  IS  THE  LOCAL  IMPORTANCE  OF  WATER   TRANSPORTATION? 

Materials.  Reports  of  the  United  States  Department  of  Commerce  and  Labor  dealing  with, 
quantities  of  materials  shipped  by  water,  and  the  sources  and  destinations  of  these  materials; 
reports  or  data  from  individual  steamship  companies  regarding  number  of  boats  in  use  through 
a  given  river  or  from  a  given  port,  the  amount  of  material  shipped,  its  nature,  source,  and  desti- 
nation ;  statements  from  local  merchants  regarding  the  nature,  source,  and  amount  of  goods  they 
receive  by  water  transportation. 

Directions.  If  the  local  community  is  affected  by  water  transportation,  discover  what  proportion 
of  goods  shipped  to  or  from  the  place  travels  by  water,  what  kinds  of  goods  are  more  frequently 
sent  by  water,  what  the  cost  is  per  ton  by  rail  and  by  water,  and  how  the  time  needed  for  delivery 
by  water  compares  with  the  time  by  rail. 

What  is  the  importance  of  water  transportation  to  your  community  ? 

Additional  problems.  What  influence  did  waterways  have  upon  the  establishment  of  New  York  City  ? 
of  Philadelphia  ?  of  San  Francisco  ?  of  New  Orleans  ?  of  St.  Louis  ?  of  Pittsburgh  ?  of  Seattle  ?  , 

What  cities  or  towns  of  your  immediate  community  are  there  whose  location  was  affected  by  waterways  ? 


[84] 


EXERCISE  61 
WHAT  IS  THE  RELATION  BETWEEN  WATER  SUPPLY  AND  DISEASE? 

Materials.  Data  given  in  Figs.  79,  81,  and  82  in  the  "  Elements  of  General  Science " ;  any 
additional  similar  data  which  are  available. 

Directions.  The  above  question  may  be  answered  by  study  of  the  death  rate  from  typhoid  fever 
in  relation  to  the  character  of  water  supply. 

Examine  Figs.  79,  81,  and  82  in  the  textbook.  Explain  in  full  to  what  extent  typhoid  appears 
to  be  a  controllable  disease  and  how  far  proper  water  supply  may  assist  in  controlling  it.  Give  the 
facts  on  which  you  base  your  opinion. 

Additional  problems.    How  do  the  leading  American  and  European  cities  compare  relative  to  propor- 
tionate deaths  from  typhoid  ?    How  may  any  difference  be  explained  ? 
Are  rivers  likely  to  be  the  best  sources  of  water  supply? 


[85] 


EXERCISE  61 A 
WHAT  IS  THE  SIGNIFICANCE  OF  THE  LOCAL  DEATH  HATE  FROM  TYPHOID? 

Materials.  Local  records  regarding  number  of  cases  of  sickness  and  death  from  typhoid.  These 
records  should  be  available  in  the  office  of  the  local  health  officers,  and  those  covering  a  period  of 
years  will  be  needed. 

Directions.  Secure  the  local  death  rate  from  typhoid  if  possible.  Consult  the  board  of  health  or 
health  officer.  If  there  are  no  such  officials,  consult  the  physicians  or  the  state  board  of  health.  The 
same  authority  should  be  able  to  give  you  the  typhoid  rate  in  a  number  of  other  places.  How  does 
your  community  compare  with  others  ?  If  its  rate  is  not  so  low  as  some  others,  try  to  learn  why. 

Additional  problem.  What  is  the  relation  of  flies  to  distribution  of  typhoid  ?  Would  there  be  danger  of 
securing  typhoid  germs  from  flies  if  all  typhoid  material  from  persons  ill  with  typhoid  were  sterilized  ? 
What  are  the  reasons  for  the  campaign  to  prevent  the  reproduction  of  flies  ? 


[86] 


EXERCISE   61 B 

WHAT  IS  THE  CHARACTER  OF  THE  LOCAL  WATER  SUPPLY? 

Materials.  Data  regarding  the  local  water  supply,  the  pump,  pumping  plant,  source  of  waterr 
methods  of  carrying  water,  and  care  in  its  use. 

Directions.  If  there  is  a  municipal  water  system,  visit  the  pumping  station.  Learn  from  what 
kind  of  source  the  water  comes ;  what  precautions  are  taken  to  protect  it  from  contamination  or  to 
purify  it ;  whether  the  supply  is  sufficient  and  the  cost  such  that  all  citizens  can  use  it  freely.  Find 
out  also  whether  tests  of  the  quality  of  the  water  have  been  made,  and  how  much  is  really  known,  and 
how  much  assumed,  regarding  its  healthfulness. 

Are  the  citizens  in  the  habit  of  attempting  home  purification  by  filtering,  boiling,  or  other  means? 

If  some  families  secure  water  from  wells,  visit  some  of  these  localities  and  note  what  precautions 
are  taken  to  protect  the  wells  from  contamination  by  surface  water,  cesspools,  stables,  etc.  Are  these 
precautions  likely  to  be  effective  ? 

What  is  your  opinion  of  the  probable  healthfulness  of  drinking  waters  in  your  community  ?  How 
could  conditions  be  improved  ? 

Additional  problems.  What  are  the  chief  methods  of  securing  adequate  water  supply  in  other  communi- 
ties near  you  ?  in  the  leading  cities  of  the  United  States  ? 

Is  it  better  and  more  economical  for  each  family  to  be  depended  upon  to  purify  its  water  or  for  the 
community  to  do  this  for  all  ? 


[87] 


EXERCISE  62 

HOW  IS  SEWAGE  DISPOSED  OF  IN  YOUR  COMMUNITY? 

Materials.    Data  and  observations  upon  the  local  methods  of  sewage  disposal. 

Directions.  Does  your  community  have  a  municipal  sewerage  system  ?  If  so,  describe  its  princi- 
pal features.  Are  most  of  the  houses  connected  with  the  system  ?  Is  it  important  that  all  should  be 
connected  ?  What  is  the  final  disposition  made  of  the  sewage  ?  Is  this  disposition  safe  as  far  as 
your  community  is  concerned  ?  Does  it  menace  the  health  of  any  other  community  ? 

If  there  is  no  sewerage  system  in  your  community,  why  not  ?  Would  the  installation  of  one  be 
an  important  public  improvement? 

Prepare  a  summary,  stating  the  principal  needs  of  your  community  with  reference  to  this  matter. 


EXERCISE  63 

HOW  ARE  PULLEYS  USED  AS  MACHINES,  AND  WHAT  ARE  THE  ADVANTAGES  OF 
DIFFERENT   SYSTEMS  OF  PULLEY  ARRANGEMENT? 

Materials.    Some  single  and  double  pulleys  ;  a  sensitive  spring  balance ;  weights  ;  some  small  cord. 

Directions.  Arrange  a  pulley,  spring  balance,  and  weight  as  shown 
in  the  figure  at  the  right  of  the  diagram.  The  weight  should  be  100 
grams  or  200  grams.  Attach  the  spring  balance  and  raise  it  through  a 
known  distance,  noting  and  recording  at  the  same  time  the  distance 
through  which  the  weight  rises.  Now  raise  and  lower  the  balance  sev- 
eral times,  taking  as  many  readings  while  raising  as  while  lowering. 
Average  the  readings.  This  is  the  reading  that  should  be  secured  if 
there  were  no  friction.  Why  ?  Keep  a  record  of  all  your  measurements 
and  readings.  Tabulate  the  averages  in  the  blanks  given  below. 

Arrange  an  apparatus  as  shown  in  the  central  figure  and  again  make 
record  of  your  results. 

Do  the  same  with  the  arrangement  as  shown  at  the  left. 

Having  secured  your  data  as  above,  compare  the  force  applied  at 
the  end  of  the  cord,  the  weight  lifted,  and  the  number  of  strands  of  cord 
supporting  the  weight;  and  from  this  state  (1)  the  mechanical  advan- 
tage of  the  pulley  system  you  are  using ;  and  (2)  the  rule  whereby  one 
may  always  tell  from  inspection  of  any  pulley  system  what  advantage 
it  will  give.  This  last  statement  should  not  be  made  until  the  results  secured  by  all  members  of 
the  class  have  been  tabulated  on  the  board  and  compared. 


r      > 

w 


ARRANGEMENT  OF  PULLEYS 

NUMBER  1 

NUMBER  2 

NUMBER  3 

Average  force  used  in  raising     ...          . 

Average  force  used  in  lowering  . 

Average  up-and-down  readings   

How  much  greater  is  weight  than  force  

Strands  of  cord  supporting  weight  

Additional  problems.  What  is  the  advantage  of  using  pulleys  in  lifting  hay  when  stacking  it  or  put- 
ting it  into  barns  ? 

If  a  piano  weighing  1000  pounds  is  to  be  moved  from  the  street  level  to  the  fourth  floor  of  a  build- 
ing 60  feet  from  the  street  level,  and  two  men  are  to  pull  a  total  of  250  pounds  in  lifting  the  piano,  what 
arrangement  of  pulleys  and  ropes  will  enable  them  to  lift  the  piano  (friction  being  neglected)  ? 


[89] 


EXERCISE  64 

HOW  TO  MEASUEE  THE  WORK  DONE  BY  THE  FORCE  APPLIED  IN  A  PULLEY 
SYSTEM  IN  RAISING  A  KNOWN  WEIGHT  A  GIVEN  DISTANCE 

Materials.    Data  from  Exercise  63. 

Directions.   Tabulate  your  results  from  Exercise  63,  in  the  first  arrangement  of  pulleys,  as  follows 


Weight  lifted    

Distance  through  which  lifted      

cm 

Force  applied  upward      

a111- 

Distance  through  which  force  is  applied   

cm. 

Calculate  in  centimeter  grams  the  work  done  by  the  force  applied  to  lift  the  weight  a  given 
distance  for  the  first  pulley  arrangement  in  Exercise  63.  These  calculations  should  be  made  accord- 
ing to  directions  given  in  the  textbook. 

Additional  problems.  Calculate  the  work  done  in  lifting  the  weight  through  the  same  distance  as  above 
by  the  second  arrangement  in  Exercise  63. 

Make  calculations  for  the  third  arrangement  in  Exercise  63. 

Compare  the  amount  of  work  done  in  the  three  cases. 

Compare  also  the  force  applied  and  the  distance  through  which  the  force  is  applied. 

What  advantage,  if  any,  is  secured  by  using  the  first  arrangement  ?  Do  the  other  arrangements  offer 
any  advantages  ? 


[91] 


EXERCISE  65 
HOW  MUCH  WORK  IS  DONE  UPON  THE  WEIGHT  (WORK  OUT)  IN  EXERCISE  63? 

Materials.    Data  from  Exercise  63. 

Directions.    Secure  from  the  first  pulley  arrangement  in  Exercise  63  the  following  data: 


The  weight  lifted  

nm. 

Distance  the  weight  is  lifted    

cm 

Calculate  the  work  done  upon  the  weight. 

Additional  problems.  In  a  manner  similar  to  the  above  determine  the  amount  of  work  accomplished 
upon  the  weight  if  it  is  lifted  the  same  distance  by  use  of  each  of  the  three  arrangements  of  pulleys.  Does 
the  work  accomplished  differ  in  each  of  the  three  cases  ? 

Can  you  determine  the  amount  of  work  done  in  the  second  additional  problem  in  Exercise  63  ? 


[93] 


EXERCISE  66 
WHAT  IS  THE  EFFICIENCY  OF  A  PULLEY  SYSTEM? 

Materials.    Data  from  the  two  preceding  exercises. 

Directions.    Secure  from  the  two  preceding  exercises  the  following  data : 


Useful  work  out     

Total  work  in    

What  percentage  of  the  work  in  is  secured  in  work  out  ?  Under  what  conditions  could  work  out 
equal  work  in  ?  What  would  be  the  percentage  of  efficiency  when  work  out  equals  work  in  ? 

Additional  problems.  How  do  you  account  for  the  fact  that  the  amount  of  work  done  upon  a  pulley 
system  is  greater  than  the  amount  of  work  secured  from  it  ?  What  becomes  of  the  work  wasted  ? 

Is  it  possible  to  construct  a  machine  from  which  as  much  work  or  more  work  may  be  secured  than 
the  amount  of  work  put  into  it  ?  Do  you  know  of  any  such  machines  ? 


[94] 


EXERCISE  67 

CAN  ONE  KIND  OF  ENERGY  BE  CHANGED  INTO  ANOTHER  KIND? 

Materials.  Some  wire  nails  or  small  pieces  of  iron  wire ;  a  piece  of  iron  or  a  stone  to  serve  as  an 
anvil ;  a  hammer ;  some  copper  wire  ;  a  rubber  or  ebony  rod ;  a  piece  of  flannel  cloth. 

Directions.  By  holding  a  nail  or  wire  in  the  hands,  note  its  temperature.  Place  the  nail  or  wire 
on  an  anvil  or  heavy  piece  of  iron  and  strike  it  several  blows  with  a  hammer.  Now  pick  up  the  nail 
or  wire  and  note  its  temperature.  How  do  you  account  for  the  change  in  temperature  ? 

Bend  a  copper  or  iron  wire  several  times  and  then  feel  the  part  where  the  bending  took  place. 
Explain  your  result. 

Write  your  answer  to  the  above  question,  giving  the  results  of  the  experiments  and  stating  your 
conclusion. 

Additional  problems.  Rub  a  rod  of  rubber  or  ebony,  or  a  fountain  pen,  with  a  piece  of  flannel,  and  then 
bring  it  to  your  ear.  What  kind  of  energy  was  present  on  the  rod  ?  How  did  it  come  to  be  there  ? 
Rub  the  rod  again  and  bring  it  near  some  very  small  scraps  of  paper.  What  is  the  result? 

Why  does  an  ungreased  wagon  or  carriage  axle  become  hot  when  used  ? 

When  sawing  wood,  does  the  saw  become  heated  ?   Does  the  wood  become  heated  ?   Why  ? 

How  did  uncivilized  tribes  of  men  start  their  fires  ?  What  principle  is  involved  in  this  method  of 
starting  fires  ?  Can  you  start  a  fire  in  the  same  way  ? 


[95] 


EXERCISE  68 
WHAT  IS  THE  PBINCIPLE  OF  THE  STEAM  ENGINE  ? 

Materials.  A  model  of  a  steam  engine,  a  toy  engine,  or  a  visit  to  a  steam  engine.  If  a  model 
is  not  available,  the  diagram  on  page  184  of  the  "  Elements  of  General  Science  "  should  be  used ; 
also,  diagrams  furnished  by  manufacturing  firms  will  be  helpful. 

Directions.  Examine  a  model  of  a  steam  engine  if  one  is  at  hand,  and  learn  how  it  works. 
Make  a  drawing  of  the  principal  parts  of  the  engine,  and  label  all  parts  to  show  how  steam  enters 
and  leaves  the  cylinder  and  how  the  piston  is  affected.  Indicate  by  arrows  the  direction  of  the 
steam.  How  is  the  energy  transmitted  to  the  wheels  of  the  engine  ?  In  labeling  your  drawing 
and  in  writing  any  additional  notes,  consult  the  drawing  in  the  textbook  for  proper  names  of  parts. 

If  no  model  is  at  hand,  examine  the  cylinder  of  an  engine  and  its  valves  and  piston,  to  learn 
how  it  works.  If  neither  the  model  nor  the  engine  is  available,  make  a  drawing  similar  to  that  in 
the  text  and  explain  in  your  own  words  how  such  an  engine  works. 

Additional  problems.    When  the  steam  leaves  the  engine,  do  you  think  all  of  its  energy  has  been  used  ? 
What  is  the  importance  of  the  use  of  steam  engines  in  industries  ?    How  many  kinds  of  steam  engines 
do  you  know  ? 


[96] 


EXERCISE  69 
WHAT  IS   THE  NATURE  OF  THE  PARTICLES  WHICH  MAKE  UP  THE  SOIL? 

Materials.     Glass  tubing  ^  inch  in  diameter  and  2  feet  or  more  in  length ;  cork  stoppers ;  soil. 

Directions.  Close  one  end  of  a  glass  tube  with  a  cork  stopper.  Different  students  may  perform 
the  following  experiment  by  use  of  different  kinds  of  soils.  Mix  some  soil  with  water  to  the  con- 
sistency of  a  thin  mud,  and  pour  in  enough  of  the  mixture  to  fill  the  lower  end  of  the  tube  3  or  4 
inches.  Add  water  to  fill  the  tube.  Close  the  upper  end  with  a  cork  stopper,  invert  the  tube,  and 
stand  it  in  a  vertical  position.  Watch  the  particles  as  they  settle  through  the  water. 

What  differences  are  there  in  the  materials  which  settle  first  and  those  which  settle  later  ?  Why 
do  some  particles  settle  before  others  ?  Describe  the  sediment  with  reference  to  the  various-sized 
particles  and  the  parts  of  the  sediment  in  which  the  particles  are  too  small  to  be  seen  with  the  un- 
aided eye.  Do  you  suppose  that  there  may  be  some  of  the  particles  which  have  not  yet  settled  ?  If 
so,  where  are  they  and  why  have  they  not  settled  ?  If  allowed  to  stand  for  several  days,  will  all 
particles  settle  ? 

Do  the  samples  of  soil  used  contain  both  rock  materials  and  organic  materials  ? 

Additional  problems.  If  a  very  long  tube  (5  or  6  feet)  is  used,  a  more  complete  separation  of  materials 
will  be  made.  Such  a  demonstration  will  prove  instructive. 

If  a  microscope  is  available,  small  pieces  of  soil  should  be  studied  under  magnification.  Such  studies 
will  enable  students  to  determine  the  form  and  structure  of  soil  particles. 


[97] 


EXERCISE  69  A 

WHAT    IS  THE  CHARACTER  OF  THAT  PART  OF  THE  SOIL  IN  WHICH  NO  PARTICLES 

CAN  BE  SEEN  WITH  THE  UNAIDED  EYE? 

Materials.  A  microscope ;  some  of  the  muddy  water  and  finest  of  the  soil  particles  from  the 
preceding  experiment. 

Directions.  Place  a  drop  of  the  muddy  water  from  the  preceding  experiment  on  a  glass  slide,  and 
examine  with  the  low  power  of  the  microscope.  (Do  not  use  the  high  power  of  the  microscope  unless 
so  directed  by  the  teacher.)  Examine  also  a  very  little  of  the  top  part  of  the  sediment  mixed  with 
water  on  the  slide.  There  should  be  only  enough  sediment  to  make  the  water  on  the  slide  appear 
cloudy.  Examine  a  third  sample  from  that  part  of  the  sediment  in  which  very  small  particles  are 
visible  to  the  naked  eye. 

Describe  the  material  in  each  case,  and  state  what  is  shown  regarding  the  structure  of  soil. 

Additional  problems.   Are  there  small  soil  particles  which  seem  to  differ  from  the  large  ones  only  in  size  ? 
Are  there  small  particles  which  differ  from  large  ones  in  their  nature  as  well  as  in  size  ? 
Does  a  fertile  soil  usually  contain  more  or  fewer  of  the  fine  soil  particles  than  do  poor  soils  ? 


[98] 


EXERCISE  70 

HOW  MUCH  WATER  MAY  BE  HELD  BY  SOIL? 

Materials.    Glass  dishes  ;  balances ;  drying  oven,  radiator,  or  stove  ;  soil. 

Directions.  For  this  exercise  soil  should  be  used  which  is  directly  from  out  of  doors.  Weigh  a 
small  dish,  fill  it  with  the  soil,  and  weigh  again.  Set  the  dish  in  a  dry,  warm  place  and  weigh  at 
intervals  as  long  as  the  soil  continues  to  lose  water  as  indicated  by  a  decrease  in  weight.  At  the 
last  it  should  be  placed  in  a  drying  oven  at  a  temperature  slightly  above  the  boiling  point.  If  an 
oven  is  not  available,  a  radiator  or  stove  may  be  used,  but  the  results  will  not  be  so  accurate. 
Tabulate  your  results  as  follows: 


Weight  of  dish       

Weight  of  soil  and  dish       

Weight  of  soil  

Loss  of  weight  (equals  evaporated  water)      

Weight  of  dry  soil      

Water  is  equal  to  what  per  cent  of  the  dry  soil      

Save  the  soil  and  keep  it  dry  for  a  later  experiment.  Note  that  the  percentages  in  this  and  the 
following  exercises  are  all  calculated  with  reference  to  dry  soil. 

Additional  problems.  Take  samples  of  soil  from  the  first  2  inches  of  the  surface,  from  a  depth  of  from  6 
to  8  inches,  and  from  a  depth  of  from  14  to  16  inches.  Determine  the  relative  percentages  of  water  in  soil 
at  the  different  depths. 

Saturate  a  soil  with  water ;  then  determine  what  percentage  of  water  it  contains. 

When  a  plant  wilts  because  it  cannot  longer  secure  water  from  the  soil,  is  the  soil  perfectly  dry  ? 


[99] 


EXERCISE  70  A 
WHAT   IS   THE  WATER-RETAILING  CAPACITY  OF  DIFFERENT:  #.$03$,  OF ^S 

Materials.    Glass  tubes  used  in  Exercise  69  ;  cork  stoppers.  >«£  >V  >  »'A§ 

Directions.  Fasten  a  glass  tube  in  a  vertical  position.  Close  the  bottom  with  a  stopper  which 
has  had  a  notch  cut  on  one  side  to  allow  water  to  leak  out.  Put  a  piece  of  blotting  paper  in  the 
bottom  of  the  tube  on  the  stopper,  if  necessary,  to  hinder  the  soil  from  falling  through  the  hole. 

Fill  the  tube  two  thirds  full  of  dry  soil,  the  weight  of  which  has  been  ascertained.  Press  the 
soil  down  lightly.  Pour  in  measured  quantities  of  water  (distilled  water  if  possible)  from  time  to 
time,  until  the  soil  is  soaked  to  the  bottom.  Catch  the  water,  if  any,  that  niters  through.  When 
the  water  has  ceased  to  come  through,  measure  it  and  compare  with  the  amount  poured  into  the 
tube.  Calculate  the  amount  of  water  retained  per  gram  of  soil. 

Several  different  types  of  soil  should  be  used  by  different  members  of  the  class  and  final  results 
compared.  If  soils  containing  much  clay  are  used,  the  water  will  pass  through  very  slowly. 

Additional  problems.     Do  different  kinds  of  soil  have  different  capacity  for  water  ? 
What  relation  is  there  between  capacity  for  water  and  drainage  of  soils  ? 


L 101 J 


EXERCISE  71 
1^  THERE  ANY   SOLUBLE  MATERIAL  IN  THE  SOIL? 

Materials     Fertile  sail;  a  large  funnel;  filter  paper;  distilled  water;  a  glass  dish. 

Directions.  Fold  and  place  filter  paper  against  the  inner  surface  of  the  funnel ;  then  fill  the 
funnel  with  soil.  Place  the  funnel  with  its  tube  above  a  clean  glass  dish,  pour  distilled  water 
upon  the  soil,  allowing  the  water  plenty  of  time  to  pass  through  the  soil  and  the  filter  paper  into 
the  dish  below.  Set  the  dish  in  a  warm  place  and  evaporate  to  dryness.  Explain  the  presence  of 
anything  which  remains  in  the  dish  after  the  water  has  evaporated. 

Additional  problem.    Is  there  danger  of  soils  losing  fertility  through  drainage  ? 


[102] 


EXERCISE  72 

WHAT  IS  THE  AMOUNT  OF  ORGANIC  MATTER  IN  SOILS? 

Materials.  Samples  of  dry  soil,  such  as  resulted  from  Exercise  70  ;  a  metal  pan  ;  Bunsen  burner 
or  a  large  alcohol  lamp. 

Directions.  The  pan  should  be  weighed  before  the  soil  is  put  in,  and  also  with  the  soil,  the 
weights  being  recorded.  Heat  the  soil  to  a  red  heat  over  any  convenient  flame,  and  continue  until 
all  the  dark  material  appears  to  be  burned.  Weigh  again  when  cool.  Tabulate  as  follows: 


Weight  of  pan  

AVei°°ht  of  pan  and.  soil  

\Vei°"ht  of  soil  

Loss  by  burnin0'  {equals  organic  matter)        

Percentage  of  organic  matter  

Additional  problem.  Secure  samples  of  soil  from  a  swamp  or  peat  bog,  also  from  a  sandy  region  and  a 
river  flood  plain ;  determine  the  percentage  of  organic  matter  as  above ;  compare  and  explain  differences 
in  these  percentages.  Does  there  appear  to  be  any  relation  between  soil  fertility  and  amount  of  organic 
matter  in  soils  ? 


[103] 


EXERCISE  73 

HOW  ARE   SOILS    FOKMED? 

Materials.  The  local  environment ;  soil-survey  reports  bearing  upon  local  soils ;  discussions 
found  in  library  materials. 

Directions.  An  excursion  should  be  made  into  the  adjacent  country  to  study  the  soils.  River- 
bottom  lands  and  uplands  should  furnish  contrasting  types  of  soils.  Differences  in  both  crops  and 
natural  vegetation  in  correspondence  with  soil  differences  may  be  seen.  Visit  a  rocky  ridge  or  ravine 
and  study  formation  of  soil  by  weathering,  plant  action,  and  stream  work.  If  the  region  is  within  the 
glaciated  area,  look  for  evidences  of  glaciation  and  glacial  soils. 

Find  out  whether  the  area  about  the  school  has  been  surveyed  by  the  Bureau  of  Soils,  Depart- 
ment of  Agriculture,  Washington,  D.C.,  and  if  so,  secure  a  copy  of  the  report.  This  will  give  map 
and  details  regarding  soil  types.  The  details  of  all  such  studies  will  change  with  the  locality  and 
must  be  left  to  the  pupils  and  teacher. 

Additional  problem.  How  many  types  of  soils  are  there  in  your  locality  ?  Can  you  determine  the  causes 
of  the  differences  in  these  soils  ?  How  do  these  soils  differ  with  reference  to  production  of  crops  ? 


[104] 


EXERCISE  74 
HOW   DOES  EROSION  AFFECT   SOILS? 

Materials.    Banks  and  riffles  of  a  lake,  river,  or  ditch. 

Directions.  This  study  is  best  carried  out  by  a  field  visit  to  a  running  stream,  a  lake  shore,  or 
a  hillside  where  ravines  have  been  formed.  An  open  drainage  ditch  will  usually  furnish  a  good  basis 
for  this  work. 

Observe  the  running  water  to  determine  whether  it  is  carrying  any  soil  particles.  Does  rapidly 
running  water  carry  more  material  or  larger  material  than  slowly  running  water?  Where  does  the 
material  come  from  ?  What  becomes  of  this  material  ?  How  does  the  carrying  power  of  water 
change  with  changes  in  its  rate  of  flow  ?  What  evidences  upon  this  question  are  there  along  banks 
and  riffles  of  lakes,  streams,  and  ditches  ? 

Additional  problems.  Arrange  an  erosion  model  in  a  sink  in  the  following  manner :  Fill  one  end  of  the 
sink  with  sandy  or  gravelly  soil ;  close  the  outlet  of  the  sink  by  use  of  a  stopper  through  which  a  short 
glass  tube  is  inserted  so  that  an  inch  or  two  of  water  will  stand  in  that  end  of  the  sink  before  the  water 
overflows  ;  by  use  of  a  tube  allow  a  small  stream  of  water  to  run  very  slowly  upon  the  soil  farthest  from 
the  outlet.  Observe  the  development  of  channels,  and  the  deposit  of  materials. 

If  in  an  open  field  erosion  is  allowed  to  continue  unhindered,  what  results  will  follow  ? 

Is  it  the  better  or  poorer  parts  of  the  soil  which  are  usually  lost  by  erosion  ? 


[105] 


EXERCISE  75 
CAN  THE  ROOTS  AND  STUMP  OF  A  PLANT  FORCE  WATER  UPWARD  ? 

Materials.  A  plant  with  a  stem  about  -|  inch  in  diameter  (a  potted  plant  or  one  growing  out  of 
doors  will  serve  for  the  exercise)  ;  glass  tube  with  small  opening ;  rubber  tubing  of  size  to  fit  closely 
over  the  stem  and  glass  tubing ;  small  cord  or  copper  wire. 

Directions.  Arrange  apparatus  as  follows:  Cut  off  the  top  of  the  plant  about  2  inches  above 
the  ground.  To  the  stump  of  the  stem  which  is  connected  with  the  roots  attach  a  glass  tube  by 
means  of  a  short  piece  of  rubber  tubing,  and  support  the  glass  tube  in  a  vertical  position.  It  may  be 
best  to  insure  a  tight  joint  by  wrapping  the  tube  tightly  with  cord  or  wire.  A  glass  tube  with  a 
small  bore  will  give  more  striking  results.  Water  the  soil  freely  and  observe  the  apparatus  at  inter- 
vals of  a  few  hours  to  see  if  water  is  being  forced  out  of  the  cut  end  of  the  stem.  If  water  is  forced 
upward,  determine  the  amount  and  the  rate  of  rise. 

Additional  problem.  If  a  grapevine  is  cut  in  the  springtime  it  "  bleeds."  Why  ?  When  maple  trees 
are  tapped,  what  is  the  source  of  the  water  which  comes  from  the  wound  ? 


[100] 


EXERCISE  76 
HOW  DOES  A  PLANT  ABSORB  WATER? 

Materials.  A  short-stemmed  thistle  tube  or  a  metal  cup  (known  as  the  Lyon  Osmometer),  such 
as  is  shown  on  page  235  of  "  Elements  of  General  Science " ;  glass  tubing ;  rubber  tubing ;  small 
cord  or  copper  wire ;  some  thick  sirup,  sugar  solution,  or  salt  solution ;  parchment  paper,  or  animal 
bladder,  or  sausage  casings. 

Directions.  Close  the  stem  of  the  thistle  tube  or  metal  cup  and  place  the  cup  with  the  stem 
downward ;  pour  the  sirup  or  other  thick  solution  into  the  cup  and  fasten  the  membrane  securely 
over  the  opening  of  the  cup ;  turn  the  cup  with  the  stem  upward  and  open  the  stem ;  by  means  of 
rubber-tubing  connections  fasten  a  long  glass  tube  to  the  stem  of  the  cup ;  stand  the  cup  in  a  dish 
of  pure  water  and  fasten  the  tube  securely ;  observe  the  apparatus  at  intervals  for  three  or  four  days 
and  record  observations.  How  are  the  results  of  this  experiment  similar  to  those  of  Exercise  75  ? 
How  different  ?  In  what  ways  does  this  experiment  explain  how  plants  secure  their  water  ? 

Additional  problems.  Bore  a  hole  in  the  top  of  a  beet  or  carrot ;  place  sugar  in  the  hole  until  it  is 
almost  full ;  stopper  the  hole  with,  a  one-holed  rubber  stopper,  a  glass  tube  having  first  been  inserted  ;  set 
the  apparatus  in  a  vessel  of  water ;  and  support  the  glass  tube  in  an  upright  position.  Observe  as  in  the 
above  experiment. 

When  a  strong  salt  solution,  such  as  that  from  an  ice-cream  freezer,  is  poured  upon  the  lawn,  the  plants 
upon  which  it  is  poured  usually  die.  Why  ? 

What  is  the  explanation  of  the  common  practice  of  putting  a  handful  of  salt  upon  the  cut  sterns  or 
roots  of  weeds  ? 


[107] 


EXERCISE  77 
WHAT  ARE  ROOT  HAIRS? 

Materials.    Drinking-glasses;  filter  paper;  seeds  of  radish,  mustard,  or  oats. 

Directions.  Cut  a  strip  of  filter  paper  4  inches  wide  and  2  inches  longer  than  the  circumfer- 
ence of  the  glass  at  its  top.  Fold  the  paper  lengthwise  with  each  fold  2  inches  wide.  Turn 
and  crease  one  fold  again,  thus  making  a  short  fold  each  side  of  which  is 
1  inch  in  width.  With  a  needle  or  pin  perforate  the  crease  of  the  short  fold 
in  many  places,  and  place  seeds  in  this  fold.  Place  the  filter  paper  with  the 
wide  fold  innermost  around  the  upper  inner  wall  of  the  drink  ing-glass,  allow- 
ing the  ends  to  fit  together.  Pour  water  into  the  glass  until  the  lower  part  of 
the  wide  fold  is  wet.  The  water  will  then  cause  the  filter  paper  to  adhere  to 
the  glass  and  will  moisten  the  seeds.  Observe  from  day  to  day,  and  as  they 
develop  describe  the  roots  and  root  hairs  with  reference  to  general  appearance, 
length,  diameter  of  hairs,  location  of  hairs  on  roots,  and  abundance  of  hairs. 

Additional  problems.  If  a  microscope  is  available,  mount  some  of  the  root  hairs,  together  with  the  root, 
from  which  they  grow,  and  make  a  detailed  study,  showing  the  exact  relation  which  exists  between  the 
root  hairs  and  the  surface  cells  of  the  root.  Determine  where  the  young  root  hairs  are  developing.  How 
do  they  grow  ?  Can  you  estimate  the  proportionate  surface  exposure  of  root  hairs  as  compared  with  that 
of  the  roots  from  which  they  grow  ? 

Plant  seeds  such  as  those  used  above  in  dishes  of  moist  sawdust  or  sand ;  when  the  young  plants 
have  developed  until  a  good  supply  of  root  hairs  are  formed,  carefully  pull  up  some  of  the  plants.  To 
'what  parts  of  the  root  system  is  most  soil  attached  ?  What  holds  the  soil  ?  What  is  meant  by  "  anchorage 
in  the  soil  "  ? 


[109] 


EXERCISE  78 
WHAT  IS  THE  PATH  OF  WATER  IN  PLANT  STEMS? 

Materials.  Freshly  cut  leafy  stems  of  both  soft  and  woody  plants ;  red  ink  or  water  which 
has  been  colored  by  addition  of  eosin  or  other  coloring  material. 

Directions.  Stand  freshly  cut  leafy  stems  in  a  colored  solution.  Very  leafy  stems,  if  placed  in 
a  sunny  location  with  good  circulation  of  air,  may  be  ready  for  examination  in  half  an  hour.  In 
many  cases  it  will  be  well  to  allow  the  material  to  stand  until  the  next  day. 

Examine  the  stems  by  cutting  across  the  stem  at  intervals  or  by  peeling  off  the  surface.  If 
blanched  celery,  yellow  coleus,  or  other  light-colored  plants  are  used,  the  stems  will  be  sufficiently 
transparent  to  show  the  red  color  without  cutting.  Can  the  course  of  the  solution  be  traced  into 
the  leaves  ?  Are  there  definite  tissues  through  which  the  solution  passes  ?  Diagram  a  cross  section 
of  the  stem  and  a  surface  view  of  a  leaf  to  show  any  point  observed  regarding  definite  tissues 
through  which  water  passes. 

Additional  problem.  How  would  the  passage  of  water  in  a  woody  plant  be  affected  if  a  ring  of  bark  were 
removed  from  the  stem  ?  What  would  be  the  effect  if  the  ring  included  the  bark  and  all  of  the  new  wood  ? 


[Ill] 


EXERCISE  79 
WHAT   FOOD   MATERIALS  ARE   PRESENT   IN   PLANTS'.' 

Materials.  The  following  are  convenient  for  this  exercise :  potato,  turnip,  carrot,  radish,  apple, 
orange,  rice,  beans,  oat  grain,  wheat  grain,  corn  grain,  or  the  products  of  these,  as  oatmeal,  flour, 
commercial  starch,  etc.;  iodine  solution;  Fehling's  solution;  nitric  acid;  ammonia;  some  test  tubes. 

Directions.    The  tests  for  food  substances  which  may  be  made  most  readily  are  the  following : 

a.  Starch.    Crush  or  scrape  some  of  the  material  to  be  investigated,  and  boil  it  in  water  in  a  test 
tube.    When  cool,  add  iodine  and  note  the  resulting  color.    If  commercial  starch  is  used,  first  the  re- 
actions may  be  seen  with  material  that  is  known  to  be  starch,  and  later  tests  for  the  presence  of  starch 
in  other  materials  will  be  made  more  accurately. 

b.  Grape  sugar.    Crush  or  scrape,  add  water,  boil,  add  1  or  2  cubic  centimeters  of  Fehling's  solu- 
tion, and  boil  again.   If  grape  sugar  is  present,  the  solution  will  soon  be  clouded  by  a  red  precipitate, 
which  will  settle  to  the  bottom. 

c.  Protein.    Crush  or  scrape  the  material  and  boil  in  water  to  which  a  few  drops  of  nitric  acid 
have  been  added.    A  yellow  color  indicates  protein,  and  this  is  changed  to  an  orange  by  the  addition 
of  ammonia.    Since  most  of  the  plant  proteins  encountered  are  not  soluble,  the  color  will  appear  upon 
the  fragments  rather  than  in  the  solution. 

In  the  above  experiments  record  your  results  in  the  blanks  given  below,  checking  for  each  material 
the  food  substances  which  are  found  to  be  present: 


MATKIUAI,  TKSTKI> 


Additional  problems  lor  this  exercise  may  !•<•  added  indefinitely  by  testing  such  plant  materials  as  are 
available. 


[112] 


EXERCISE  80 

IS   STARCH  SOLUBLE  IN  WATER  ? 

Materials.    Powdered  starch ;  iodine  solution ;  test  tubes. 

Directions.  Put  a  small  amount  of  starch  in  cold  water  in  a  test  tube.  Add  sufficient  iodine 
solution  to  eolor  the  starch,  and  shake  the  mixture  thoroughly.  Set  it  aside  and  observe  from  time 
to  time,  as  the  starch  settles,  to  see  whether  any  of  the  starch  remains  permanently  and  evenly 
distributed  throughout  the  water,  as  will  be  the  case  if  the  starch  is  dissolved. 

In  another  test  tube  place  a  small  amount  of  starch  in  water  and  heat  to  a  boiling  temperature. 
When  cool,  add  a  few  drops  of  iodine  solution.  Set  it  aside  until  the  following  day.  If  the  starch  is 
dissolved  the  liquid  will  remain  colored  throughout,  but  if  the  starch  is  not  dissolved  part  or  all  of 
the  liquid  will  be  clear. 

Additional  problems.  When  using  starch  in  laundry  work  the  water  in  which  the  starch  is  placed  is 
usually  heated.  Why  ? 

From  the  above  experiments  do  you  infer  that  starch  can  pass  readily  from  one  part  of  a  plant  to 
another  part? 


[114] 


EXERCISE  81 


Materials.    Test  tubes ;    starch   paste ;    malted    barley   or   barley   grains ;    iodine    solution    and 

Fehling's    solution. 

Directions.  Partly  fill  a  large  test  tube  or  a  cup  with  starch  paste  made  by  boiling  a  half 
teaspoonful  of  starch  in  a  half  pint  of  water. 

Prepare  a  malt  extract  by  securing  some  dry  malted  barley  and  grinding  it  in  a  mortar  or 
a  coffee  grinder;  soak  1  or  2  tablespoonfuls  of  the  barley  in  a  cupful  of  water  for  an  hour; 
filter  off  the  water,  which  with  the  substances  in  solution  is  the  malt  extract. 

If  malted  barley  cannot  be  had,  soak  some  fresh  barley  grains  in  water  for  from  ten  to  twelve 
hours,  pour  off  the  water,  and  place  the  barley  in  a  closely  covered  dish  in  a  warm  place  to 
germinate.  When  the  sprouts  are  an  eighth  of  an  inch  long,  crush  the  barley,  soak  in  water,  and 
treat  as  above. 

To  a  test  tube  of  starch  paste  add  1  or  2  cubic  centimeters  of  the  malt  extract.  Allow  the 
mixture  to  stand  for  at  least  half  an  hour,  preferably  in  a  warm  place.  It  may  stand  overnight  with 
advantage.  Test  a  small  sample  for  starch.  Test  another  sample  for  grape  sugar. 

What  change  has  taken  place  as  to  the  amount  of  starch  ?  of  grape  sugar  ?  How  do  you  account 
for  these  changes  ? 

NOTE.  There  is  always  some  sugar  in  the  malted  barley,  and  this  will  be  dissolved  in  the  malt  extract. 
Sugar  is,  therefore,  added  to  the  starch  paste  with  the  malt  extract,  but  if  a  small  amount  of  the  extract  is 
used,  the  amount  of  sugar  added  will  not  be  great.  Some  of  the  pupils  may  wish  to  test  the  malt  ex- 
tract diluted  with  water  instead  of  starch  paste,  to  determine  whether  or  not  all  the  sugar  in.  the  above 
test  was  originally  in  the  malt.  They  should  devise  their  own  method. 

Additional  problems.  Put  some  powdered  starch  in  cold  water  in  a  test  tube,  add  a  small  amount  of  malt 
extract,  and  leave  in  a  warm  place  for  twenty-four  hours  or  more.  Test  with  Fehling's  solution  to  see  if 
sugar  is  present. 

If  a  microscope  is  available,  examine  starch  grains  which  were  used  in  the  preceding  problem  and 
compare  them  with  starch  grains  which  have  not  been  treated  with  malt.  Do  any  of  the  grains  show 
evidence  that  they  have  been  partly  dissolved  ? 


[115] 


EXERCISE  82 

HOW  IS   FOOD  DISTRIBUTED   THROUGH  THE  HUMAN  BODY?  — THE  FLOW  OF 

BLOOD   IN  THE  VEINS 

Directions.  Allow  the  arm  to  hang  downward ;  grip  the  arm  tightly  above  the  elbow  and  note 
the  location  and  appearance  of  the  veins  of  the  lower  arm.  Then  releasing  the  pressure  on  the 
upper  arm,  hold  the  arm  pointing  upward  and  note  the  change  in  the  appearance  of  the  veins. 
Account  for  this  difference.  Place  your  finger  on  a  prominent  vein  and  note  the  appearance  of  the 
vein  on  both  sides  of  the  finger.  Can  you  in  this  way  determine  the  direction  of  the  flow?  Do 
you  feel  any  pulse  beat  in  the  veins? 


[117] 


EXERCISE  83 
THE  FLOW  OF  BLOOD  IN  THE  ARTERIES 

Directions.  Most  of  the  arteries  lie  deep  in  the  tissues,  but  they  may  be  recognized  by  their 
V  beat;"  Examine  the  right-hand  wrist  with  the  tip  of  the  finger  and  locate  the  artery  on  the  palm 
side  of  the  wrist  near  the  base  of  the  thumb.  Locate  the  arteries  of  both  wrists.  Count  the  number 
of  beats  per  minute.  Repeat  to  verify.  Find  also  the  carotid  artery  in  the  side  of  the  neck,  the 
small  artery  at  either  side  of  the  nose  just  below  the  eye,  and  the  artery  just  in  front  of  the  ear. 
What  is  the  average  number  of  heartbeats  per  minute  for  your  entire  class  ?  What  are  the  greatest 
individual  variations  ? 

Additional  problems.  When  an  injury  results  in  cutting  a  large  blood  vessel,  how  can  you  distinguish 
whether  it  is  an  artery  or  a  vein  ? 

If  an  artery  were  cut  at  the  elbow,  where  should  the  bandage  be  placed  in  order  to  stop  the  bleeding  ? 


[118] 


EXERCISE  84 
OF  WHAT  DOES  THE  BLOOD  CONSIST? 

Materials.    A  compound  microscope  ;  a  cover  glass ;  vaseline  ;  a  needle  ;  alcohol. 

Directions.  This  experiment  should  be  done  by  the  instructor  as  a  demonstration.  Sterilize  a 
sharp  needle  by  holding  it  in  a  flame  for  a  few  moments.  Wash  the  ball  of  the  middle  finger  of 
the  left  hand  with  alcohol.  Tie  a  piece  of  cloth  quite  securely  around  the  first  joint,  and  then 
with  a  quick  thrust  of  the  needle  puncture  the  skin.  A  drop  of  blood  will  quickly  collect.  This 
should  be  transferred  to  a  glass  slide.  A  cover  glass  which  has  had  vaseline  applied  to  its  edges 
should  be  placed  over  the  drop  in  order  to  seal  it.  Can  you  distinguish  the  liquid  of  the  blood  from 
the  solid  bodies  (corpuscles)  ?  What  is  the  nature  of  the  corpuscles  ?  Where  is  most  of  the  coloring 
matter  of  the  blood  ? 

Additional  problem.  If  prepared  slides  with  corpuscles  properly  stained  are  available,  make  a  detailed 
study  of  both  red  and  white  corpuscles,  and  make  drawings  to  illustrate  their  structure. 


[119] 


EXERCISE  85 
HOW  DOES  THE  BLOOD  CIRCULATE  THROUGH  THE  CAPILLARIES? 

Materials.  A  compound  microscope ;  a  frog ;  a  board  such  as  a  chalk-box  cover,  with  a  glass 
slide  fastened  over  a  V-shaped  notch  in  one  end  of  the  board ;  chloroform  or  ether. 

Directions.  Anaesthetize  a  frog  by  placing  it  in  a  small  jar  and  adding  a  few  cubic  centimeters 
of  chloroform  or  ether.  When  the  frog  is  completely  under  the  influence  of  the  chloroform  or 
ether,  so  that  it  will  not  withdraw  its  foot  when  extended,  place  one  of  its  feet  under  the  micro- 
scope so  that  a  part  of  the  web  is  in  focus,  and  hold  it  in  position.  Observe  the  flow  of  the  blood, 
the  color  of  the  blood,  and  any  other  points  which  you  can  see.  What  seems  to  be  the  rate  of  flow 
of  the  blood  in  capillaries  as  compared  with  arteries  and  veins  ?  As  the  frog  comes  from  under 
the  influence  of  the  anaesthetic,  is  there  any  change  in  the  rate  of  flow  of  the  blood  ? 

Additional  problem.  Mount  a  small  fish  or  a  tadpole  so  that  the  microscope  shows  the  thin  flesh  of 
the  tail,  and  observe  the  circulation  through  the  capillaries.  This  experiment  may  be  used  instead  of 
thev_above,  no  anaesthetic  being  necessary. 


[120] 


EXERCISE  86 
WHAT  ARE   THE  VALUES   OF  DIFFERENT  KINDS  OF  FOODS? 

Materials.    The  data  presented  on  page  243  of  the  "  Elements  of  General  Science." 

Directions.     It  is  commonly  supposed  that  an   average   man  needs   for  his  daily  food  .supply 
approximately  the  following  amounts  of  the  different  kinds  of  food: 

Protein 4£  ounces 

Fats 2  ounces 

Carbohydrates 17  ounces 

With  these  amounts  as  the  basis  of  calculations,  solve  the  following  problems,  referring  when 
necessary  to  the  table  on  page  243  of  the  textbook : 

a.  If  one  should  eat  potatoes  only,  how  much  would  he  need  to  consume  in  a  day  in  order  to 
secure  enough  protein  to  meet  his  day's  requirement  ? 

b.  How  much  milk  would  be  necessary  to  supply  the  needed  protein  if  it  were  used  exclusively 
as  the  day's  food? 

c.  Determine  the  same  point,  assuming  that  bread  is  the  sole  source  of  food. 

d.  How  much  rice  would  be  required  for  a  day's  protein  food  if  nothing  else  were  eaten  ? 

e.  Which  of  the  foods  are  the  best-balanced  with  respect  to  the  amounts  of  the  three  materials  ? 


[121] 


EXERCISE  87 
WHAT   ARE  THE  STAGES   IN   THE  DEVELOPMENT   OF  THE  FROG'S  EGG? 

Materials.  Fresh  eggs  of  the  frog  or  toad  (these  may  be  secured  in  early  spring,  the  toad's 
eggs  usually  appearing  a  little  later  than  those  of  the  frog)  ;  large  aquarium  jars ;  hand  magnify- 
ing glasses. 

Directions.  Place  the  eggs  of  the  frog  or  toad  in  an  aquarium  in  shallow  water.  Observe  them 
from  day  to  day,  noting  early  stages  of  development.  Some  of  the  eggs  may  be  examined  from 
day  to  day  under  the  low  power  of  a  microscope.  The  following  stages  may  be  observed : 

a.  If  the  eggs  are  secured  very  soon  after  they  are  laid  it  will  be  possible  to  see,  with  a  hand 
magnifier  or  under  the  low  power  of  a  microscope,  some  which  have  divided  into  2  cells,  4  cells, 
or  a  larger  number  of  cells. 

6.  At  a  later  period  the  original  single  egg  cell  has  divided  into  such  a  large  number  that  the 
individual  cells  of  the  mass  cannot  be  separately  distinguished  by  use  of  the  magnifier. 

c.  The  mass  of  cells  produced  by  the  egg  becomes  elongated  instead  of  spherical.    This  is  called 
the  embryo. 

d.  The  embryo  continues  to   elongate ;    head   and  tail   may  be  distinguished ;    eyes   and  other 
organs  appear. 

e.  The  young   animal  frees  itself  from  the  surrounding  jelly,  swims   through  the  water,  and 
usually  attaches  itself  to  floating  objects  or  to  the  walls  of  the  aquarium.    At  this  stage  it  has 
conspicuous  gills  (breathing  organs). 

Record  and  describe  all  the  changes  which  you  have  observed  in  the  development  of  the  egg. 

Additional  problems.    Can  you  discover  how  to  distinguish  frog's  eggs  from,  toad's  eggs  ? 
In  what  kinds  of  situations  do  these  animals  lay  their  eggs  ? 
At  approximately  what  dates  are  frog's  and  toad's  eggs  laid  in  your  region  ? 

Newts  and  salamanders  are  animals  which  are  related  to  frogs  and  toads  in  structure  and  habits.  If  you 
can  find  their  eggs,  these  animals  may  be  grown  in  aquaria,  as  may  frogs  and  toads. 


[  122  ] 


EXERCISE  88 
THE  GROWTH  AND  DEVELOPMENT  OF  A  TADPOLE 

Materials.    The  materials  of  the  preceding  exercise. 

Directions.  Observe  the  tadpoles  of  the  preceding  experiment  during  several  weeks.  Record  your 
observations,  including  the  following  points  and  questions : 

a.  Changes  in  form. 

b.  Feeding  habits. 

c.  Growth. 

d.  Appearance  of  legs. 

e.  Disappearance  of  tail. 

f.  Evidences  of  air-breathing  in  later  stages. 

g.  Emergence  from  water. 

At  what  stage  in  the  development  of  the  tadpole  do  the  gills  disappear  ?  When  does  the  animal 
cease  to  attach  itself  constantly  to  some  solid  object  ?  Which  of  the  legs  appears  first  ?  Are  the  first 
legs  and  the  tail  used  at  the  same  time  in  swimming  ?  What  becomes  of  the  -tail  ? 

Additional  problems.    What  is  the  food  material  of  frogs  and  toads  when  they  live  on  land  ? 

Of  what  economic  importance  are  toads  ? 

Is  the  practice  of  destroying  toads  an  intelligent  practice  ? 


[124] 


EXERCISE  88  A 
THE  DEVELOPMENT   OF  THE  BIRD  EMBRYO  DURING   THE  HATCHING   OF   THE  EGG 

Materials.    Two  dozen  hen's  eggs ;  an.  incubator. 

Directions.  Place  at  least  two  dozen  hen's  eggs  in  an  incubator  which  has  previously  been  in 
operation  until  it  is  properly  regulated.  Open  an  egg  on  at  least  each  of  the  following  days  of  the 
incubating  period :  first  day ;  second ;  third ;  fifth ;  eighth ;  twelfth ;  sixteenth.  On  the  first  day 
note  the  germ  cell,  or  fertilized  egg,  lying  close  to  the  yolk,  it  being  recognized  by  a  reddish  ring 
about  it.  In  the  other  observations  determine  what  changes  have  taken  place  in  the  eggs. 

Additional  problems.  Why  will  eggs  usually  not  hatch  after  they  have  been  subjected  to  sudden  and 
great  changes  in  temperature  ?  Why  will  eggs  not  hatch  after  they  have  been  in  cold  storage  ? 

How  do  you  account  for  the  fact  that  in  a  nest  of  young  robins  the  birds  hatch  on  successive  days, 
while  in  a  nest  of  quail  or  domestic  fowls  the  young  birds  usually  all  hatch  on  the  same  day  ? 


[125] 


EXERCISE  89 
THE  STRUCTURE  OF  A  SEED  AND  OF  THE  YOUNG  PLANT 

Materials.  Seeds  of  bean,  corn,  or  peanut ;  sawdust,  sand,  or  common  soil ;  earthen  pots  or  small 
wooden  boxes. 

Directions.  Plant  seeds  of  bean,  corn,  or  peanut  at  least  two  weeks  before  it  is  intended  to  make 
this  study.  If  the  seeds  are  planted  in  a  glass  jar  near  the  sides,  the  sides  being  darkened  by  use  of 
a  black  cloth,  the  growth  may  be  observed  during  the  process.  Observe  the  plantings  from  time  to 
time  and  record  all  facts  of  interest  as  the  young  plants  "come  up."  When  the  plants  have  from 
two  to  four  leaves,  make  your  final  study  and  description.  At  this  time  the  young  stem  and 
roots,  as  well  as  the  leaves,  will  have  assumed  definite  form  and  their  characteristic  positions. 

Soak  seeds  in  water  for  about  twenty-four  hours  and  examine  them  to  discover  how  many  and 
what  structures  found  in  the  seedling  may  be  found  also  in  the  seed.  Examine  the  seeds  for 
evidence  of  stored  food.  What  is  the  function  of  this  food  in  the  development  of  the  young  plant  ? 

Additional  problems.  Plant  ten  or  twelve  different  kinds  of  seeds,  and  as  they  grow  determine  the 
nature  and  variations  in  the  seed  leaves  of  these  plants. 

By  use  of  a  very  sharp  knife  remove  the  seed  leaves  from  some  seedlings  as  soon  as  the  seed  leaves 
appear  above  the  soil,  and  determine  what  effect  this  has  upon  the  young  plants. 


[126] 


EXERCISE  90 

HOW  KAPIDLY  MAY  PLANTS  AND  ANIMALS   INCKEASE  UNDER  ENTIRELY 

FAVORABLE  CONDITIONS? 

Materials.  Ears  of  corn ;  heads  of  wheat  or  oats ;  seed  pods  of  any  common  plants ;  data 
regarding  number  of  eggs  laid  by  a  robin  and  a  toad. 

Directions.  Determine  how  rapidly  given  plants  or  animals  would  increase  in  given  lengths  of 
time,  if  all  seeds  should  grow  each  year  in  case  of  plants  or  if  all  the  young  of  animals  should 
mature. 

It  is  suggested  that  each  pupil  perform  but  one  or  two  of  the  determinations  given  below,  and 
that  the  results  of  all  determinations  be  made  available  to  the  entire  class. 

a.  Indian  corn.    Count  the  rows  and  number  of  grains   in   a  row  on  one  ear.    Estimate  the 
number  of  grains  on  the  ear.     Calculate  the  descendants  in  the  fifth  generation. 

b.  Wheat.    Ascertain  the  number  of  grains  in  a  head  and  suppose  that  there  are  five  heads  to 
each  plant.    Calculate  the  number  of  grains  in  the  fifth  generation. 

c.  Robin.    Assuming  that  a  female  robin  will  lay  four  eggs  and  that  one  half  of  the  new  birds 
will  be  females,  calculate  the  number  of  robins  at  the  end  of  ten  years  if  all  eggs  hatch  and  no 
birds  die. 

d.  Toad.    A  female  toad  may  lay  as  many  as  11,000  eggs.     Assuming  8000  as  a  fair  average 
and  that  one  half  the  young  toads  will  be  females,  calculate  the  number  of  toads  from  a  sirtgle 
pair  at  the  end  of  four  generations  if  all  the  eggs  hatch  and  no  toads  die. 

Additional  problems.  Assuming  that  an  average  toad  will  weigh  a  quarter  of  a  pound,  what  would 
be  the  weight  of  the  four  generations  of  toads  according  to  the  above  estimate? 

Why  do  not  plants  or  animals  really  increase  as  rapidly  as  indicated  by  the  above  calculations  ? 


[127] 


EXERCISE  91 
HOW  DO   EARS  OF  CORN  DIFFER   IN   THE  NUMBER  OF  GRAINS   THEY   HAVE? 

Materials.    A  supply  of  ears  of  corn,  so  that  each  pupil  may  have  one  ear. 

Directions.  Each  pupil  should  calculate  the  number  of  grains  on  one  ear.  In  case  grains  have 
been  lost,  determine  how  many  were  lost  and  add  this  number  to  the  number  counted.  Write  the 
total  upon  the  board,  and  also  copy  in  your  notebook  the  totals  of  all  the  other  pupils.  Underline 
the  largest  and  smallest  numbers  and  leave  all  the  numbers  for  further  use. 

Additional  problems.  Do  most  of  the  ears  used  in  the  calculations  come  nearest  to  the  smallest  number, 
to  the  largest  number,  or  midway  between  ? 

If  you  were  selecting  one  ear  for  planting  from  all  those  used  in  the  calculations,  which  one  would 
you  select  ?  What  qualities  lead  you  to  make  your  selection  ? 


[129] 


EXERCISE  92 

HOW  DO  EARS  OF  CORN  DIFFER  IN  WEIGHT? 

Materials.    Same  as  in  Exercise  91. 

Directions.  Each  pupil  should  weigh  accurately  one  ear  of  corn  and  record  the  weight  on  the 
board  at  the  side  of  the  number  of  grains  on  this  same  ear.  Copy  all  the  weights  in  your  notebook. 
Underline  the  heaviest  and  lightest  ears.  Are  these  ears  the  same  ones  which  have  respectively  the 
largest  and  smallest  number  of  grains? 

Additional  problems.    Are  most  ears  heavy,  light,  or  medium  ? 

Is  your  choice  of  the  best  ear  for  planting  changed  by  the  above  calculation  ? 


[130] 


EXERCISE  93 

WHAT  IS  THE  RELATION  BETWEEN  THE  WEIGHT  OF  THE  GRAINS  AND  THAT  OF 

THE  COB  IN  EARS  OF  CORN? 

Materials.    Same  as  in  Exercises  91  and  92. 

Directions.  Weigh  the  ear.  Shell  the  grains  from  the  cob.  Be  careful  to  lose  none.  Weigh  the 
grains  and  record  the  weight,  using  the  blanks  given  below.  Weigh  the  cob.  Add  the  two  weights, 
and  if  they  do  not  correspond  with  the  total  weight  of  the  ear  (Exercise  92),  try  to  discover  your 
error. 


Weight  of  ear    

Weight  of  grains    

Weight  of  cob   

Sum  of  grains  and  cob    .... 

Difference      

Place  the  weights  of  grains  and  cob  on  the  board  at  the  sides  of  the  corresponding  figures  for 
each  ear.  Underline  the  ear  having  the  largest  weight  of  grains ;  largest  weight  of  cob ;  smallest 
weight  of  grains ;  smallest  weight  of  cob. 

Additional  problems.  What  percentage  of  the  total  weight  of  the  ear  is  the  weight  of  the  grains  ? 
Record  this  percentage  at  the  side  of  corresponding  numbers  for  the  ear.  Underline  the  highest  and  the 
lowest  percentage  of  grains  to  total  weight.  In  the  light  of  all  facts  shown,  which  ear  would  you  now 
select  as  the  best  for  planting  ? 

Could  you  select  from  the  above  data  any  combination  of  characteristics  which  would  appear  better 
than  any  combination  which  was  found  ? 


[131] 


EXERCISE  94 


ARE  VARIATIONS  IN  PARENTS  TRANSMITTED  TO  OFFSPRING? 

Materials.  The  table  given  below  shows  the  height  of  928  persons  whose  records  were  studied 
by  Francis  Galton.  It  is  so  arranged  that  the  heights  of  these  individuals  may  be  compared  with  the 
heights  of  their  parents,  and  the  inheritance  of  stature  may  thus  be  seen. 

Directions.  In  the  third  horizontal  space  from  the  top  the  figures  given  indicate  the  size-groups 
in  which  the  children  are  classified.  The  vertical  column  at  the  left  (column  1)  gives  the  heights  of 
the  parents,  the  heading  "  mid-parental  height "  meaning  the  middle  point  between  the  heights  of  the 
two  parents  in  a  family. 


MID-PARENTAL 
HEIGHT 

HEIGHTS  OF  ADULT  CHILDREN 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

61.2 
and 
below 

62.2 

63.2 

64.2 

65.2 

66.2 

67.2 

68.2 

69.2 

70.2 

71.2 

72.2 

73.2 

74.2 
and 
above 

MEAN  or 
CHILDREN 

a 

72.5 
and  above 

1 

3 

72.95 

b 

72.5 

1 

2 

1 

2 

7 

2 

4 

71.4 

c 

71.5 

1 

8 

4 

3 

5 

10 

4 

9 

2 

2 

69.9 

d 

70.5 

1 

1 

1 

1 

3 

12 

18 

11 

7 

4 

8 

3 

69.5 

e 

69.5 

1 

16 

4 

17 

27 

20 

33 

25 

20 

11 

4 

5 

68.6 

f 

68.5 

1 

7 

11 

16 

25 

31 

34 

48 

21 

18 

4 

3 

68.0 

2 

67.5 

3 

5 

14 

15 

36 

38 

28 

38 

19 

11 

4 

67.6 

h 

66.5 

8 

3 

5 

2 

17 

17 

14 

13 

4 

67.1 

i 

65.5 

1 

9 

5 

7 

11 

11 

7 

7 

5 

2 

1 

66.8 

j 

64.5 

1 

1 

4 

4 

1 

5 

5 

2 

65.6 

k 

63.5 
and  below 

1 

2 

4 

1 

2 

2 

1 

1 

65.6 

In  column  16  at  the  right  the  figures  in  each  space  represent  the  average  height  of  all  children 
of  parents  of  the  heights  indicated  in  the  corresponding  space  in  column  1.  The  other  figures  of  the 
table  indicate  the  distribution  of  the  children.  The  way  in  which  the  table  is  read  is  indicated  by 
the  following  examples: 

Column  3  shows  that  among  the  seven  persons  whose  heights  were  near  62.2  inches  there  were 
three  from  families  in  which  the  mid-parental  height  was  67.5  ;  three  from  families  with  a  parental 
average  of  66.5 ;  and  one  from  a  family  in  which  the  parental  average  was  64.5. 

Line  b  shows  that  in  all  the  families  in  which  the  mid-parental  height  was  72.5  inches  one 
child  had  a  height,  when  adult,  of  about  68.2  inches;  two  were  69.2  inches  tall;  one  was  70.2; 
two  were  71.2 ;  seven  belonged  to  the  72.2  group ;  two  belonged  to  the  73.2  group ;  and  four  were 
taller  than  any  of  these. 

Examine  line  f.  Observe  and  state  how  wide  is  the  variation.  Note  how  many  children  are 
taller  than  their  parents,  how  many  are  shorter,  and  how  many  are  nearly  of  the  parental  height. 

[138] 


EXERCISE  94  (Continued) 

Do  you  find  that  many  of  the  children  closely  resemble  the  parents  in  height  ?  Before  you  draw 
any  conclusions  look  over  lines  c  and  j  and  other  lines,  to  see  whether  the  relations  you  find  in 
line  f  are  generally  true. 

So  far  as  you  can  determine  by  this  study,  what  do  you  think  about  the  probable  average 
resemblance  of  a  child  to  its  parents?  Try  to  write  your  conclusion  in  the  form  of  a  general  rule 
about  the  likeness  of  the  offspring  to  parents. 

Additional  problems.  Compare  the  average  heights  of  parents  (column  1,  b  to  j)  with  average  heights 
of  their  children  (column  16).  Find  the  difference  between  these  figures  in  each  horizontal  line,  marking 
the  differences  by  the  plus  sign  (+)  if  the  children  average  taller  than  their  parents  and  by  the  minus  sign 
(— )  if  they  are  shorter.  Do  the  children  of  unusually  tall  parents  average  more  unusual  than  their  parents  or 
less  unusual  ?  Are  children  of  unusually  tall  parents  taller  than  the  average  of  all  ?  Are  any  of  them  taller 
than  their  parents  ?  Make  the  same  study  regarding  the  unusually  short  persons.  In  general,  do  the 
children  of  unusual  parents  average  as  unusual  as  the  parents  ? 

If  the  rule  of  inheritance  shown  above  holds  good  for  such  characteristics  as  mental  ability,  moral 
tendencies,  tendencies  toward  insanity  and  feeble-mindedness,  what  is  the  advantage  of  being  "  well-born"  ? 


134 


YE  06993 


700941 


UNIVERSITY  OF  CALIFORNIA  UBRARY 


